## GSocket

GSocket — Low-level socket object

## Synopsis

    #include <gio/gio.h>

                        GSocket;
    gboolean            (*GSocketSourceFunc)                (GSocket *socket,
                                                             GIOCondition condition,
                                                             gpointer user_data);
    enum                GSocketType;
    enum                GSocketProtocol;
    enum                GSocketMsgFlags;
    struct              GInputVector;
    struct              GOutputVector;
    GSocket *           g_socket_new                        (GSocketFamily family,
                                                             GSocketType type,
                                                             GSocketProtocol protocol,
                                                             GError **error);
    GSocket *           g_socket_new_from_fd                (gint fd,
                                                             GError **error);
    gboolean            g_socket_bind                       (GSocket *socket,
                                                             GSocketAddress *address,
                                                             gboolean allow_reuse,
                                                             GError **error);
    gboolean            g_socket_listen                     (GSocket *socket,
                                                             GError **error);
    GSocket *           g_socket_accept                     (GSocket *socket,
                                                             GCancellable *cancellable,
                                                             GError **error);
    gboolean            g_socket_connect                    (GSocket *socket,
                                                             GSocketAddress *address,
                                                             GCancellable *cancellable,
                                                             GError **error);
    gboolean            g_socket_check_connect_result       (GSocket *socket,
                                                             GError **error);
    gssize              g_socket_receive                    (GSocket *socket,
                                                             gchar *buffer,
                                                             gsize size,
                                                             GCancellable *cancellable,
                                                             GError **error);
    gssize              g_socket_receive_from               (GSocket *socket,
                                                             GSocketAddress **address,
                                                             gchar *buffer,
                                                             gsize size,
                                                             GCancellable *cancellable,
                                                             GError **error);
    gssize              g_socket_receive_message            (GSocket *socket,
                                                             GSocketAddress **address,
                                                             GInputVector *vectors,
                                                             gint num_vectors,
                                                             GSocketControlMessage ***messages,
                                                             gint *num_messages,
                                                             gint *flags,
                                                             GCancellable *cancellable,
                                                             GError **error);
    gssize              g_socket_receive_with_blocking      (GSocket *socket,
                                                             gchar *buffer,
                                                             gsize size,
                                                             gboolean blocking,
                                                             GCancellable *cancellable,
                                                             GError **error);
    gssize              g_socket_send                       (GSocket *socket,
                                                             const gchar *buffer,
                                                             gsize size,
                                                             GCancellable *cancellable,
                                                             GError **error);
    gssize              g_socket_send_to                    (GSocket *socket,
                                                             GSocketAddress *address,
                                                             const gchar *buffer,
                                                             gsize size,
                                                             GCancellable *cancellable,
                                                             GError **error);
    gssize              g_socket_send_message               (GSocket *socket,
                                                             GSocketAddress *address,
                                                             GOutputVector *vectors,
                                                             gint num_vectors,
                                                             GSocketControlMessage **messages,
                                                             gint num_messages,
                                                             gint flags,
                                                             GCancellable *cancellable,
                                                             GError **error);
    gssize              g_socket_send_with_blocking         (GSocket *socket,
                                                             const gchar *buffer,
                                                             gsize size,
                                                             gboolean blocking,
                                                             GCancellable *cancellable,
                                                             GError **error);
    gboolean            g_socket_close                      (GSocket *socket,
                                                             GError **error);
    gboolean            g_socket_is_closed                  (GSocket *socket);
    gboolean            g_socket_shutdown                   (GSocket *socket,
                                                             gboolean shutdown_read,
                                                             gboolean shutdown_write,
                                                             GError **error);
    gboolean            g_socket_is_connected               (GSocket *socket);
    GSource *           g_socket_create_source              (GSocket *socket,
                                                             GIOCondition condition,
                                                             GCancellable *cancellable);
    GIOCondition        g_socket_condition_check            (GSocket *socket,
                                                             GIOCondition condition);
    gboolean            g_socket_condition_wait             (GSocket *socket,
                                                             GIOCondition condition,
                                                             GCancellable *cancellable,
                                                             GError **error);
    gboolean            g_socket_condition_timed_wait       (GSocket *socket,
                                                             GIOCondition condition,
                                                             gint64 timeout,
                                                             GCancellable *cancellable,
                                                             GError **error);
    gssize              g_socket_get_available_bytes        (GSocket *socket);
    void                g_socket_set_listen_backlog         (GSocket *socket,
                                                             gint backlog);
    gint                g_socket_get_listen_backlog         (GSocket *socket);
    gboolean            g_socket_get_blocking               (GSocket *socket);
    void                g_socket_set_blocking               (GSocket *socket,
                                                             gboolean blocking);
    gboolean            g_socket_get_keepalive              (GSocket *socket);
    void                g_socket_set_keepalive              (GSocket *socket,
                                                             gboolean keepalive);
    guint               g_socket_get_timeout                (GSocket *socket);
    void                g_socket_set_timeout                (GSocket *socket,
                                                             guint timeout);
    void                g_socket_set_ttl                    (GSocket *socket,
                                                             guint ttl);
    guint               g_socket_get_ttl                    (GSocket *socket);
    gboolean            g_socket_get_broadcast              (GSocket *socket);
    void                g_socket_set_broadcast              (GSocket *socket,
                                                             gboolean broadcast);
    gboolean            g_socket_get_option                 (GSocket *socket,
                                                             gint level,
                                                             gint optname,
                                                             gint *value,
                                                             GError **error);
    gboolean            g_socket_set_option                 (GSocket *socket,
                                                             gint level,
                                                             gint optname,
                                                             gint value,
                                                             GError **error);
    GSocketFamily       g_socket_get_family                 (GSocket *socket);
    int                 g_socket_get_fd                     (GSocket *socket);
    GSocketAddress *    g_socket_get_local_address          (GSocket *socket,
                                                             GError **error);
    GSocketProtocol     g_socket_get_protocol               (GSocket *socket);
    GSocketAddress *    g_socket_get_remote_address         (GSocket *socket,
                                                             GError **error);
    GSocketType         g_socket_get_socket_type            (GSocket *socket);
    gboolean            g_socket_speaks_ipv4                (GSocket *socket);
    GCredentials *      g_socket_get_credentials            (GSocket *socket,
                                                             GError **error);

    gboolean            g_socket_join_multicast_group       (GSocket *socket,
                                                             GInetAddress *group,
                                                             gboolean source_specific,
                                                             const gchar *iface,
                                                             GError **error);
    gboolean            g_socket_leave_multicast_group      (GSocket *socket,
                                                             GInetAddress *group,
                                                             gboolean source_specific,
                                                             const gchar *iface,
                                                             GError **error);
    gboolean            g_socket_get_multicast_loopback     (GSocket *socket);
    void                g_socket_set_multicast_loopback     (GSocket *socket,
                                                             gboolean loopback);
    guint               g_socket_get_multicast_ttl          (GSocket *socket);
    void                g_socket_set_multicast_ttl          (GSocket *socket,
                                                             guint ttl);

## Object Hierarchy

      GObject
       +----GSocket

## Implemented Interfaces

GSocket implements GInitable.

## Properties

      "blocking"                 gboolean              : Read / Write
      "broadcast"                gboolean              : Read / Write
      "family"                   GSocketFamily         : Read / Write / Construct Only
      "fd"                       gint                  : Read / Write / Construct Only
      "keepalive"                gboolean              : Read / Write
      "listen-backlog"           gint                  : Read / Write
      "local-address"            GSocketAddress*       : Read
      "multicast-loopback"       gboolean              : Read / Write
      "multicast-ttl"            guint                 : Read / Write
      "protocol"                 GSocketProtocol       : Read / Write / Construct Only
      "remote-address"           GSocketAddress*       : Read
      "timeout"                  guint                 : Read / Write
      "ttl"                      guint                 : Read / Write
      "type"                     GSocketType           : Read / Write / Construct Only

## Description

A GSocket is a low-level networking primitive. It is a more or less direct mapping of the BSD socket API in a portable GObject based API. It supports both the UNIX socket implementations and winsock2 on Windows.

GSocket is the platform independent base upon which the higher level network primitives are based. Applications are not typically meant to use it directly, but rather through classes like GSocketClient, GSocketService and GSocketConnection. However there may be cases where direct use of GSocket is useful.

GSocket implements the GInitable interface, so if it is manually constructed by e.g. `g_object_new()` you must call `g_initable_init()` and check the results before using the object. This is done automatically in `g_socket_new()` and `g_socket_new_from_fd()`, so these functions can return `NULL`.

Sockets operate in two general modes, blocking or non-blocking. When in blocking mode all operations block until the requested operation is finished or there is an error. In non-blocking mode all calls that would block return immediately with a `G_IO_ERROR_WOULD_BLOCK` error. To know when a call would successfully run you can call `g_socket_condition_check()`, or `g_socket_condition_wait()`. You can also use `g_socket_create_source()` and attach it to a GMainContext to get callbacks when I/O is possible. Note that all sockets are always set to non blocking mode in the system, and blocking mode is emulated in GSocket.

When working in non-blocking mode applications should always be able to handle getting a `G_IO_ERROR_WOULD_BLOCK` error even when some other function said that I/O was possible. This can easily happen in case of a race condition in the application, but it can also happen for other reasons. For instance, on Windows a socket is always seen as writable until a write returns `G_IO_ERROR_WOULD_BLOCK`.

GSockets can be either connection oriented or datagram based. For connection oriented types you must first establish a connection by either connecting to an address or accepting a connection from another address. For connectionless socket types the target/source address is specified or received in each I/O operation.

All socket file descriptors are set to be close-on-exec.

Note that creating a GSocket causes the signal `SIGPIPE` to be ignored for the remainder of the program. If you are writing a command-line utility that uses GSocket, you may need to take into account the fact that your program will not automatically be killed if it tries to write to `stdout` after it has been closed.

## Details

### GSocket

    typedef struct _GSocket GSocket;

A lowlevel network socket object.

Since 2.22

### GSocketSourceFunc ()

    gboolean            (*GSocketSourceFunc)                (GSocket *socket,
                                                             GIOCondition condition,
                                                             gpointer user_data);

This is the function type of the callback used for the GSource returned by `g_socket_create_source()`.

`socket` : | the GSocket
`condition` : | the current condition at the source fired.
`user_data` : | data passed in by the user.
Returns : | it should return `FALSE` if the source should be removed.

Since 2.22

### enum GSocketType

    typedef enum {
      G_SOCKET_TYPE_INVALID,
      G_SOCKET_TYPE_STREAM,
      G_SOCKET_TYPE_DATAGRAM,
      G_SOCKET_TYPE_SEQPACKET
    } GSocketType;

Flags used when creating a GSocket. Some protocols may not implement all the socket types.

`G_SOCKET_TYPE_INVALID` | Type unknown or wrong
`G_SOCKET_TYPE_STREAM` | Reliable connection-based byte streams (e.g. TCP).
`G_SOCKET_TYPE_DATAGRAM` | Connectionless, unreliable datagram passing. (e.g. UDP)
`G_SOCKET_TYPE_SEQPACKET` | Reliable connection-based passing of datagrams of fixed maximum length (e.g. SCTP).

Since 2.22

### enum GSocketProtocol

    typedef enum {
      G_SOCKET_PROTOCOL_UNKNOWN = -1,
      G_SOCKET_PROTOCOL_DEFAULT = 0,
      G_SOCKET_PROTOCOL_TCP     = 6,
      G_SOCKET_PROTOCOL_UDP     = 17,
      G_SOCKET_PROTOCOL_SCTP    = 132
    } GSocketProtocol;

A protocol identifier is specified when creating a GSocket, which is a family/type specific identifier, where 0 means the default protocol for the particular family/type.

This enum contains a set of commonly available and used protocols. You can also pass any other identifiers handled by the platform in order to use protocols not listed here.

`G_SOCKET_PROTOCOL_UNKNOWN` | The protocol type is unknown
`G_SOCKET_PROTOCOL_DEFAULT` | The default protocol for the family/type
`G_SOCKET_PROTOCOL_TCP` | TCP over IP
`G_SOCKET_PROTOCOL_UDP` | UDP over IP
`G_SOCKET_PROTOCOL_SCTP` | SCTP over IP

Since 2.22

### enum GSocketMsgFlags

    typedef enum {
      G_SOCKET_MSG_NONE,
      G_SOCKET_MSG_OOB = GLIB_SYSDEF_MSG_OOB,
      G_SOCKET_MSG_PEEK = GLIB_SYSDEF_MSG_PEEK,
      G_SOCKET_MSG_DONTROUTE = GLIB_SYSDEF_MSG_DONTROUTE
    } GSocketMsgFlags;

Flags used in `g_socket_receive_message()` and `g_socket_send_message()`. The flags listed in the enum are some commonly available flags, but the values used for them are the same as on the platform, and any other flags are passed in/out as is. So to use a platform specific flag, just include the right system header and pass in the flag.

`G_SOCKET_MSG_NONE` | No flags.
`G_SOCKET_MSG_OOB` | Request to send/receive out of band data.
`G_SOCKET_MSG_PEEK` | Read data from the socket without removing it from the queue.
`G_SOCKET_MSG_DONTROUTE` | Don't use a gateway to send out the packet, only send to hosts on directly connected networks.

Since 2.22

### struct GInputVector

    struct GInputVector {
      gpointer buffer;
      gsize size;
    };

Structure used for scatter/gather data input. You generally pass in an array of GInputVectors and the operation will store the read data starting in the first buffer, switching to the next as needed.

gpointer `buffer`; | Pointer to a buffer where data will be written.
gsize `size`; | the available size in `buffer`.

Since 2.22

### struct GOutputVector

    struct GOutputVector {
      gconstpointer buffer;
      gsize size;
    };

Structure used for scatter/gather data output. You generally pass in an array of GOutputVectors and the operation will use all the buffers as if they were one buffer.

gconstpointer `buffer`; | Pointer to a buffer of data to read.
gsize `size`; | the size of `buffer`.

Since 2.22

### g_socket_new ()

    GSocket *           g_socket_new                        (GSocketFamily family,
                                                             GSocketType type,
                                                             GSocketProtocol protocol,
                                                             GError **error);

Creates a new GSocket with the defined family, type and protocol. If `protocol` is 0 (`G_SOCKET_PROTOCOL_DEFAULT`) the default protocol type for the family and type is used.

The `protocol` is a family and type specific int that specifies what kind of protocol to use. GSocketProtocol lists several common ones. Many families only support one protocol, and use 0 for this, others support several and using 0 means to use the default protocol for the family and type.

The protocol id is passed directly to the operating system, so you can use protocols not listed in GSocketProtocol if you know the protocol number used for it.

`family` : | the socket family to use, e.g. `G_SOCKET_FAMILY_IPV4`.
`type` : | the socket type to use.
`protocol` : | the id of the protocol to use, or 0 for default.
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | a GSocket or `NULL` on error. Free the returned object with `g_object_unref()`.

Since 2.22

### g_socket_new_from_fd ()

    GSocket *           g_socket_new_from_fd                (gint fd,
                                                             GError **error);

Creates a new GSocket from a native file descriptor or winsock SOCKET handle.

This reads all the settings from the file descriptor so that all properties should work. Note that the file descriptor will be set to non-blocking mode, independent on the blocking mode of the GSocket.

`fd` : | a native socket file descriptor.
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | a GSocket or `NULL` on error. Free the returned object with `g_object_unref()`.

Since 2.22

### g_socket_bind ()

    gboolean            g_socket_bind                       (GSocket *socket,
                                                             GSocketAddress *address,
                                                             gboolean allow_reuse,
                                                             GError **error);

When a socket is created it is attached to an address family, but it doesn't have an address in this family. `g_socket_bind()` assigns the address (sometimes called name) of the socket.

It is generally required to bind to a local address before you can receive connections. (See `g_socket_listen()` and `g_socket_accept()` ). In certain situations, you may also want to bind a socket that will be used to initiate connections, though this is not normally required.

`allow_reuse` should be `TRUE` for server sockets (sockets that you will eventually call `g_socket_accept()` on), and `FALSE` for client sockets. (Specifically, if it is `TRUE`, then `g_socket_bind()` will set the `SO_REUSEADDR` flag on the socket, allowing it to bind `address` even if that address was previously used by another socket that has not yet been fully cleaned-up by the kernel. Failing to set this flag on a server socket may cause the bind call to return `G_IO_ERROR_ADDRESS_IN_USE` if the server program is stopped and then immediately restarted.)

`socket` : | a GSocket.
`address` : | a GSocketAddress specifying the local address.
`allow_reuse` : | whether to allow reusing this address
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | `TRUE` on success, `FALSE` on error.

Since 2.22

### g_socket_listen ()

    gboolean            g_socket_listen                     (GSocket *socket,
                                                             GError **error);

Marks the socket as a server socket, i.e. a socket that is used to accept incoming requests using `g_socket_accept()`.

Before calling this the socket must be bound to a local address using `g_socket_bind()`.

To set the maximum amount of outstanding clients, use `g_socket_set_listen_backlog()`.

`socket` : | a GSocket.
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | `TRUE` on success, `FALSE` on error.

Since 2.22

### g_socket_accept ()

    GSocket *           g_socket_accept                     (GSocket *socket,
                                                             GCancellable *cancellable,
                                                             GError **error);

Accept incoming connections on a connection-based socket. This removes the first outstanding connection request from the listening socket and creates a GSocket object for it.

The `socket` must be bound to a local address with `g_socket_bind()` and must be listening for incoming connections (`g_socket_listen()`).

If there are no outstanding connections then the operation will block or return `G_IO_ERROR_WOULD_BLOCK` if non-blocking I/O is enabled. To be notified of an incoming connection, wait for the `G_IO_IN` condition.

`socket` : | a GSocket.
`cancellable` : | a `GCancellable` or `NULL`. [allow-none]
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | a new GSocket, or `NULL` on error. Free the returned object with `g_object_unref()`. [transfer full]

Since 2.22

### g_socket_connect ()

    gboolean            g_socket_connect                    (GSocket *socket,
                                                             GSocketAddress *address,
                                                             GCancellable *cancellable,
                                                             GError **error);

Connect the socket to the specified remote address.

For connection oriented socket this generally means we attempt to make a connection to the `address`. For a connection-less socket it sets the default address for `g_socket_send()` and discards all incoming datagrams from other sources.

Generally connection oriented sockets can only connect once, but connection-less sockets can connect multiple times to change the default address.

If the connect call needs to do network I/O it will block, unless non-blocking I/O is enabled. Then `G_IO_ERROR_PENDING` is returned and the user can be notified of the connection finishing by waiting for the G_IO_OUT condition. The result of the connection must then be checked with `g_socket_check_connect_result()`.

`socket` : | a GSocket.
`address` : | a GSocketAddress specifying the remote address.
`cancellable` : | a `GCancellable` or `NULL`. [allow-none]
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | `TRUE` if connected, `FALSE` on error.

Since 2.22

### g_socket_check_connect_result ()

    gboolean            g_socket_check_connect_result       (GSocket *socket,
                                                             GError **error);

Checks and resets the pending connect error for the socket. This is used to check for errors when `g_socket_connect()` is used in non-blocking mode.

`socket` : | a GSocket
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | `TRUE` if no error, `FALSE` otherwise, setting `error` to the error

Since 2.22

### g_socket_receive ()

    gssize              g_socket_receive                    (GSocket *socket,
                                                             gchar *buffer,
                                                             gsize size,
                                                             GCancellable *cancellable,
                                                             GError **error);

Receive data (up to `size` bytes) from a socket. This is mainly used by connection-oriented sockets; it is identical to `g_socket_receive_from()` with `address` set to `NULL`.

For `G_SOCKET_TYPE_DATAGRAM` and `G_SOCKET_TYPE_SEQPACKET` sockets, `g_socket_receive()` will always read either 0 or 1 complete messages from the socket. If the received message is too large to fit in `buffer`, then the data beyond `size` bytes will be discarded, without any explicit indication that this has occurred.

For `G_SOCKET_TYPE_STREAM` sockets, `g_socket_receive()` can return any number of bytes, up to `size`. If more than `size` bytes have been received, the additional data will be returned in future calls to `g_socket_receive()`.

If the socket is in blocking mode the call will block until there is some data to receive, the connection is closed, or there is an error. If there is no data available and the socket is in non-blocking mode, a `G_IO_ERROR_WOULD_BLOCK` error will be returned. To be notified when data is available, wait for the `G_IO_IN` condition.

On error -1 is returned and `error` is set accordingly.

`socket` : | a GSocket
`buffer` : | a buffer to read data into (which should be at least `size` bytes long). [array length=size][element-type guint8]
`size` : | the number of bytes you want to read from the socket
`cancellable` : | a `GCancellable` or `NULL`. [allow-none]
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | Number of bytes read, or 0 if the connection was closed by the peer, or -1 on error

Since 2.22

### g_socket_receive_from ()

    gssize              g_socket_receive_from               (GSocket *socket,
                                                             GSocketAddress **address,
                                                             gchar *buffer,
                                                             gsize size,
                                                             GCancellable *cancellable,
                                                             GError **error);

Receive data (up to `size` bytes) from a socket.

If `address` is non-`NULL` then `address` will be set equal to the source address of the received packet. `address` is owned by the caller.

See `g_socket_receive()` for additional information.

`socket` : | a GSocket
`address` : | a pointer to a GSocketAddress pointer, or `NULL`. [out][allow-none]
`buffer` : | a buffer to read data into (which should be at least `size` bytes long). [array length=size][element-type guint8]
`size` : | the number of bytes you want to read from the socket
`cancellable` : | a `GCancellable` or `NULL`. [allow-none]
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | Number of bytes read, or 0 if the connection was closed by the peer, or -1 on error

Since 2.22

### g_socket_receive_message ()

    gssize              g_socket_receive_message            (GSocket *socket,
                                                             GSocketAddress **address,
                                                             GInputVector *vectors,
                                                             gint num_vectors,
                                                             GSocketControlMessage ***messages,
                                                             gint *num_messages,
                                                             gint *flags,
                                                             GCancellable *cancellable,
                                                             GError **error);

Receive data from a socket. This is the most complicated and fully-featured version of this call. For easier use, see `g_socket_receive()` and `g_socket_receive_from()`.

If `address` is non-`NULL` then `address` will be set equal to the source address of the received packet. `address` is owned by the caller.

`vector` must point to an array of GInputVector structs and `num_vectors` must be the length of this array. These structs describe the buffers that received data will be scattered into. If `num_vectors` is -1, then `vectors` is assumed to be terminated by a GInputVector with a `NULL` buffer pointer.

As a special case, if `num_vectors` is 0 (in which case, `vectors` may of course be `NULL`), then a single byte is received and discarded. This is to facilitate the common practice of sending a single '\0' byte for the purposes of transferring ancillary data.

`messages`, if non-`NULL`, will be set to point to a newly-allocated array of GSocketControlMessage instances or `NULL` if no such messages was received. These correspond to the control messages received from the kernel, one GSocketControlMessage per message from the kernel. This array is `NULL`-terminated and must be freed by the caller using `g_free()` after calling `g_object_unref()` on each element. If `messages` is `NULL`, any control messages received will be discarded.

`num_messages`, if non-`NULL`, will be set to the number of control messages received.

If both `messages` and `num_messages` are non-`NULL`, then `num_messages` gives the number of GSocketControlMessage instances in `messages` (ie: not including the `NULL` terminator).

`flags` is an in/out parameter. The commonly available arguments for this are available in the GSocketMsgFlags enum, but the values there are the same as the system values, and the flags are passed in as-is, so you can pass in system-specific flags too (and `g_socket_receive_message()` may pass system-specific flags out).

As with `g_socket_receive()`, data may be discarded if `socket` is `G_SOCKET_TYPE_DATAGRAM` or `G_SOCKET_TYPE_SEQPACKET` and you do not provide enough buffer space to read a complete message. You can pass `G_SOCKET_MSG_PEEK` in `flags` to peek at the current message without removing it from the receive queue, but there is no portable way to find out the length of the message other than by reading it into a sufficiently-large buffer.

If the socket is in blocking mode the call will block until there is some data to receive, the connection is closed, or there is an error. If there is no data available and the socket is in non-blocking mode, a `G_IO_ERROR_WOULD_BLOCK` error will be returned. To be notified when data is available, wait for the `G_IO_IN` condition.

On error -1 is returned and `error` is set accordingly.

`socket` : | a GSocket
`address` : | a pointer to a GSocketAddress pointer, or `NULL`. [out][allow-none]
`vectors` : | an array of GInputVector structs. [array length=num_vectors]
`num_vectors` : | the number of elements in `vectors`, or -1
`messages` : | a pointer which may be filled with an array of GSocketControlMessages, or `NULL`. [array length=num_messages][allow-none]
`num_messages` : | a pointer which will be filled with the number of elements in `messages`, or `NULL`
`flags` : | a pointer to an int containing GSocketMsgFlags flags
`cancellable` : | a `GCancellable` or `NULL`. [allow-none]
`error` : | a GError pointer, or `NULL`
Returns : | Number of bytes read, or 0 if the connection was closed by the peer, or -1 on error

Since 2.22

### g_socket_receive_with_blocking ()

    gssize              g_socket_receive_with_blocking      (GSocket *socket,
                                                             gchar *buffer,
                                                             gsize size,
                                                             gboolean blocking,
                                                             GCancellable *cancellable,
                                                             GError **error);

This behaves exactly the same as `g_socket_receive()`, except that the choice of blocking or non-blocking behavior is determined by the `blocking` argument rather than by `socket`'s properties.

`socket` : | a GSocket
`buffer` : | a buffer to read data into (which should be at least `size` bytes long). [array length=size][element-type guint8]
`size` : | the number of bytes you want to read from the socket
`blocking` : | whether to do blocking or non-blocking I/O
`cancellable` : | a `GCancellable` or `NULL`. [allow-none]
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | Number of bytes read, or 0 if the connection was closed by the peer, or -1 on error

Since 2.26

### g_socket_send ()

    gssize              g_socket_send                       (GSocket *socket,
                                                             const gchar *buffer,
                                                             gsize size,
                                                             GCancellable *cancellable,
                                                             GError **error);

Tries to send `size` bytes from `buffer` on the socket. This is mainly used by connection-oriented sockets; it is identical to `g_socket_send_to()` with `address` set to `NULL`.

If the socket is in blocking mode the call will block until there is space for the data in the socket queue. If there is no space available and the socket is in non-blocking mode a `G_IO_ERROR_WOULD_BLOCK` error will be returned. To be notified when space is available, wait for the `G_IO_OUT` condition. Note though that you may still receive `G_IO_ERROR_WOULD_BLOCK` from `g_socket_send()` even if you were previously notified of a `G_IO_OUT` condition. (On Windows in particular, this is very common due to the way the underlying APIs work.)

On error -1 is returned and `error` is set accordingly.

`socket` : | a GSocket
`buffer` : | the buffer containing the data to send. [array length=size][element-type guint8]
`size` : | the number of bytes to send
`cancellable` : | a `GCancellable` or `NULL`. [allow-none]
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | Number of bytes written (which may be less than `size`), or -1 on error

Since 2.22

### g_socket_send_to ()

    gssize              g_socket_send_to                    (GSocket *socket,
                                                             GSocketAddress *address,
                                                             const gchar *buffer,
                                                             gsize size,
                                                             GCancellable *cancellable,
                                                             GError **error);

Tries to send `size` bytes from `buffer` to `address`. If `address` is `NULL` then the message is sent to the default receiver (set by `g_socket_connect()`).

See `g_socket_send()` for additional information.

`socket` : | a GSocket
`address` : | a GSocketAddress, or `NULL`. [allow-none]
`buffer` : | the buffer containing the data to send. [array length=size][element-type guint8]
`size` : | the number of bytes to send
`cancellable` : | a `GCancellable` or `NULL`. [allow-none]
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | Number of bytes written (which may be less than `size`), or -1 on error

Since 2.22

### g_socket_send_message ()

    gssize              g_socket_send_message               (GSocket *socket,
                                                             GSocketAddress *address,
                                                             GOutputVector *vectors,
                                                             gint num_vectors,
                                                             GSocketControlMessage **messages,
                                                             gint num_messages,
                                                             gint flags,
                                                             GCancellable *cancellable,
                                                             GError **error);

Send data to `address` on `socket`. This is the most complicated and fully-featured version of this call. For easier use, see `g_socket_send()` and `g_socket_send_to()`.

If `address` is `NULL` then the message is sent to the default receiver (set by `g_socket_connect()`).

`vectors` must point to an array of GOutputVector structs and `num_vectors` must be the length of this array. (If `num_vectors` is -1, then `vectors` is assumed to be terminated by a GOutputVector with a `NULL` buffer pointer.) The GOutputVector structs describe the buffers that the sent data will be gathered from. Using multiple GOutputVectors is more memory-efficient than manually copying data from multiple sources into a single buffer, and more network-efficient than making multiple calls to `g_socket_send()`.

`messages`, if non-`NULL`, is taken to point to an array of `num_messages` GSocketControlMessage instances. These correspond to the control messages to be sent on the socket. If `num_messages` is -1 then `messages` is treated as a `NULL`-terminated array.

`flags` modify how the message is sent. The commonly available arguments for this are available in the GSocketMsgFlags enum, but the values there are the same as the system values, and the flags are passed in as-is, so you can pass in system-specific flags too.

If the socket is in blocking mode the call will block until there is space for the data in the socket queue. If there is no space available and the socket is in non-blocking mode a `G_IO_ERROR_WOULD_BLOCK` error will be returned. To be notified when space is available, wait for the `G_IO_OUT` condition. Note though that you may still receive `G_IO_ERROR_WOULD_BLOCK` from `g_socket_send()` even if you were previously notified of a `G_IO_OUT` condition. (On Windows in particular, this is very common due to the way the underlying APIs work.)

On error -1 is returned and `error` is set accordingly.

`socket` : | a GSocket
`address` : | a GSocketAddress, or `NULL`. [allow-none]
`vectors` : | an array of GOutputVector structs. [array length=num_vectors]
`num_vectors` : | the number of elements in `vectors`, or -1
`messages` : | a pointer to an array of GSocketControlMessages, or `NULL`. [array length=num_messages][allow-none]
`num_messages` : | number of elements in `messages`, or -1.
`flags` : | an int containing GSocketMsgFlags flags
`cancellable` : | a `GCancellable` or `NULL`. [allow-none]
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | Number of bytes written (which may be less than `size`), or -1 on error

Since 2.22

### g_socket_send_with_blocking ()

    gssize              g_socket_send_with_blocking         (GSocket *socket,
                                                             const gchar *buffer,
                                                             gsize size,
                                                             gboolean blocking,
                                                             GCancellable *cancellable,
                                                             GError **error);

This behaves exactly the same as `g_socket_send()`, except that the choice of blocking or non-blocking behavior is determined by the `blocking` argument rather than by `socket`'s properties.

`socket` : | a GSocket
`buffer` : | the buffer containing the data to send. [array length=size][element-type guint8]
`size` : | the number of bytes to send
`blocking` : | whether to do blocking or non-blocking I/O
`cancellable` : | a `GCancellable` or `NULL`. [allow-none]
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | Number of bytes written (which may be less than `size`), or -1 on error

Since 2.26

### g_socket_close ()

    gboolean            g_socket_close                      (GSocket *socket,
                                                             GError **error);

Closes the socket, shutting down any active connection.

Closing a socket does not wait for all outstanding I/O operations to finish, so the caller should not rely on them to be guaranteed to complete even if the close returns with no error.

Once the socket is closed, all other operations will return `G_IO_ERROR_CLOSED`. Closing a socket multiple times will not return an error.

Sockets will be automatically closed when the last reference is dropped, but you might want to call this function to make sure resources are released as early as possible.

Beware that due to the way that TCP works, it is possible for recently-sent data to be lost if either you close a socket while the `G_IO_IN` condition is set, or else if the remote connection tries to send something to you after you close the socket but before it has finished reading all of the data you sent. There is no easy generic way to avoid this problem; the easiest fix is to design the network protocol such that the client will never send data "out of turn". Another solution is for the server to half-close the connection by calling `g_socket_shutdown()` with only the `shutdown_write` flag set, and then wait for the client to notice this and close its side of the connection, after which the server can safely call `g_socket_close()`. (This is what GTcpConnection does if you call `g_tcp_connection_set_graceful_disconnect()`. But of course, this only works if the client will close its connection after the server does.)

`socket` : | a GSocket
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | `TRUE` on success, `FALSE` on error

Since 2.22

### g_socket_is_closed ()

    gboolean            g_socket_is_closed                  (GSocket *socket);

Checks whether a socket is closed.

`socket` : | a GSocket
Returns : | `TRUE` if socket is closed, `FALSE` otherwise

Since 2.22

### g_socket_shutdown ()

    gboolean            g_socket_shutdown                   (GSocket *socket,
                                                             gboolean shutdown_read,
                                                             gboolean shutdown_write,
                                                             GError **error);

Shut down part of a full-duplex connection.

If `shutdown_read` is `TRUE` then the receiving side of the connection is shut down, and further reading is disallowed.

If `shutdown_write` is `TRUE` then the sending side of the connection is shut down, and further writing is disallowed.

It is allowed for both `shutdown_read` and `shutdown_write` to be `TRUE`.

One example where this is used is graceful disconnect for TCP connections where you close the sending side, then wait for the other side to close the connection, thus ensuring that the other side saw all sent data.

`socket` : | a GSocket
`shutdown_read` : | whether to shut down the read side
`shutdown_write` : | whether to shut down the write side
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | `TRUE` on success, `FALSE` on error

Since 2.22

### g_socket_is_connected ()

    gboolean            g_socket_is_connected               (GSocket *socket);

Check whether the socket is connected. This is only useful for connection-oriented sockets.

`socket` : | a GSocket.
Returns : | `TRUE` if socket is connected, `FALSE` otherwise.

Since 2.22

### g_socket_create_source ()

    GSource *           g_socket_create_source              (GSocket *socket,
                                                             GIOCondition condition,
                                                             GCancellable *cancellable);

Creates a `GSource` that can be attached to a `GMainContext` to monitor for the availibility of the specified `condition` on the socket.

The callback on the source is of the GSocketSourceFunc type.

It is meaningless to specify `G_IO_ERR` or `G_IO_HUP` in `condition`; these conditions will always be reported output if they are true.

`cancellable` if not `NULL` can be used to cancel the source, which will cause the source to trigger, reporting the current condition (which is likely 0 unless cancellation happened at the same time as a condition change). You can check for this in the callback using `g_cancellable_is_cancelled()`.

If `socket` has a timeout set, and it is reached before `condition` occurs, the source will then trigger anyway, reporting `G_IO_IN` or `G_IO_OUT` depending on `condition`. However, `socket` will have been marked as having had a timeout, and so the next GSocket I/O method you call will then fail with a `G_IO_ERROR_TIMED_OUT`.

`socket` : | a GSocket
`condition` : | a GIOCondition mask to monitor
`cancellable` : | a `GCancellable` or `NULL`. [allow-none]
Returns : | a newly allocated `GSource`, free with `g_source_unref()`. [transfer full]

Since 2.22

### g_socket_condition_check ()

    GIOCondition        g_socket_condition_check            (GSocket *socket,
                                                             GIOCondition condition);

Checks on the readiness of `socket` to perform operations. The operations specified in `condition` are checked for and masked against the currently-satisfied conditions on `socket`. The result is returned.

Note that on Windows, it is possible for an operation to return `G_IO_ERROR_WOULD_BLOCK` even immediately after `g_socket_condition_check()` has claimed that the socket is ready for writing. Rather than calling `g_socket_condition_check()` and then writing to the socket if it succeeds, it is generally better to simply try writing to the socket right away, and try again later if the initial attempt returns `G_IO_ERROR_WOULD_BLOCK`.

It is meaningless to specify `G_IO_ERR` or `G_IO_HUP` in condition; these conditions will always be set in the output if they are true.

This call never blocks.

`socket` : | a GSocket
`condition` : | a GIOCondition mask to check
Returns : | the `GIOCondition` mask of the current state

Since 2.22

### g_socket_condition_wait ()

    gboolean            g_socket_condition_wait             (GSocket *socket,
                                                             GIOCondition condition,
                                                             GCancellable *cancellable,
                                                             GError **error);

Waits for `condition` to become true on `socket`. When the condition is met, `TRUE` is returned.

If `cancellable` is cancelled before the condition is met, or if the socket has a timeout set and it is reached before the condition is met, then `FALSE` is returned and `error`, if non-`NULL`, is set to the appropriate value (`G_IO_ERROR_CANCELLED` or `G_IO_ERROR_TIMED_OUT`).

See also `g_socket_condition_timed_wait()`.

`socket` : | a GSocket
`condition` : | a GIOCondition mask to wait for
`cancellable` : | a GCancellable, or `NULL`. [allow-none]
`error` : | a GError pointer, or `NULL`
Returns : | `TRUE` if the condition was met, `FALSE` otherwise

Since 2.22

### g_socket_condition_timed_wait ()

    gboolean            g_socket_condition_timed_wait       (GSocket *socket,
                                                             GIOCondition condition,
                                                             gint64 timeout,
                                                             GCancellable *cancellable,
                                                             GError **error);

Waits for up to `timeout` microseconds for `condition` to become true on `socket`. If the condition is met, `TRUE` is returned.

If `cancellable` is cancelled before the condition is met, or if `timeout` (or the socket's "timeout") is reached before the condition is met, then `FALSE` is returned and `error`, if non-`NULL`, is set to the appropriate value (`G_IO_ERROR_CANCELLED` or `G_IO_ERROR_TIMED_OUT`).

If you don't want a timeout, use `g_socket_condition_wait()`. (Alternatively, you can pass -1 for `timeout`.)

Note that although `timeout` is in microseconds for consistency with other GLib APIs, this function actually only has millisecond resolution, and the behavior is undefined if `timeout` is not an exact number of milliseconds.

`socket` : | a GSocket
`condition` : | a GIOCondition mask to wait for
`timeout` : | the maximum time (in microseconds) to wait, or -1
`cancellable` : | a GCancellable, or `NULL`. [allow-none]
`error` : | a GError pointer, or `NULL`
Returns : | `TRUE` if the condition was met, `FALSE` otherwise

Since 2.32

### g_socket_get_available_bytes ()

    gssize              g_socket_get_available_bytes        (GSocket *socket);

Get the amount of data pending in the OS input buffer.

`socket` : | a GSocket
Returns : | the number of bytes that can be read from the socket without blocking or -1 on error.

Since 2.32

### g_socket_set_listen_backlog ()

    void                g_socket_set_listen_backlog         (GSocket *socket,
                                                             gint backlog);

Sets the maximum number of outstanding connections allowed when listening on this socket. If more clients than this are connecting to the socket and the application is not handling them on time then the new connections will be refused.

Note that this must be called before `g_socket_listen()` and has no effect if called after that.

`socket` : | a GSocket.
`backlog` : | the maximum number of pending connections.

Since 2.22

### g_socket_get_listen_backlog ()

    gint                g_socket_get_listen_backlog         (GSocket *socket);

Gets the listen backlog setting of the socket. For details on this, see `g_socket_set_listen_backlog()`.

`socket` : | a GSocket.
Returns : | the maximum number of pending connections.

Since 2.22

### g_socket_get_blocking ()

    gboolean            g_socket_get_blocking               (GSocket *socket);

Gets the blocking mode of the socket. For details on blocking I/O, see `g_socket_set_blocking()`.

`socket` : | a GSocket.
Returns : | `TRUE` if blocking I/O is used, `FALSE` otherwise.

Since 2.22

### g_socket_set_blocking ()

    void                g_socket_set_blocking               (GSocket *socket,
                                                             gboolean blocking);

Sets the blocking mode of the socket. In blocking mode all operations block until they succeed or there is an error. In non-blocking mode all functions return results immediately or with a `G_IO_ERROR_WOULD_BLOCK` error.

All sockets are created in blocking mode. However, note that the platform level socket is always non-blocking, and blocking mode is a GSocket level feature.

`socket` : | a GSocket.
`blocking` : | Whether to use blocking I/O or not.

Since 2.22

### g_socket_get_keepalive ()

    gboolean            g_socket_get_keepalive              (GSocket *socket);

Gets the keepalive mode of the socket. For details on this, see `g_socket_set_keepalive()`.

`socket` : | a GSocket.
Returns : | `TRUE` if keepalive is active, `FALSE` otherwise.

Since 2.22

### g_socket_set_keepalive ()

    void                g_socket_set_keepalive              (GSocket *socket,
                                                             gboolean keepalive);

Sets or unsets the `SO_KEEPALIVE` flag on the underlying socket. When this flag is set on a socket, the system will attempt to verify that the remote socket endpoint is still present if a sufficiently long period of time passes with no data being exchanged. If the system is unable to verify the presence of the remote endpoint, it will automatically close the connection.

This option is only functional on certain kinds of sockets. (Notably, `G_SOCKET_PROTOCOL_TCP` sockets.)

The exact time between pings is system- and protocol-dependent, but will normally be at least two hours. Most commonly, you would set this flag on a server socket if you want to allow clients to remain idle for long periods of time, but also want to ensure that connections are eventually garbage-collected if clients crash or become unreachable.

`socket` : | a GSocket.
`keepalive` : | Value for the keepalive flag

Since 2.22

### g_socket_get_timeout ()

    guint               g_socket_get_timeout                (GSocket *socket);

Gets the timeout setting of the socket. For details on this, see `g_socket_set_timeout()`.

`socket` : | a GSocket.
Returns : | the timeout in seconds

Since 2.26

### g_socket_set_timeout ()

    void                g_socket_set_timeout                (GSocket *socket,
                                                             guint timeout);

Sets the time in seconds after which I/O operations on `socket` will time out if they have not yet completed.

On a blocking socket, this means that any blocking GSocket operation will time out after `timeout` seconds of inactivity, returning `G_IO_ERROR_TIMED_OUT`.

On a non-blocking socket, calls to `g_socket_condition_wait()` will also fail with `G_IO_ERROR_TIMED_OUT` after the given time. Sources created with `g_socket_create_source()` will trigger after `timeout` seconds of inactivity, with the requested condition set, at which point calling `g_socket_receive()`, `g_socket_send()`, `g_socket_check_connect_result()`, etc, will fail with `G_IO_ERROR_TIMED_OUT`.

If `timeout` is 0 (the default), operations will never time out on their own.

Note that if an I/O operation is interrupted by a signal, this may cause the timeout to be reset.

`socket` : | a GSocket.
`timeout` : | the timeout for `socket`, in seconds, or 0 for none

Since 2.26

### g_socket_set_ttl ()

    void                g_socket_set_ttl                    (GSocket *socket,
                                                             guint ttl);

Sets the time-to-live for outgoing unicast packets on `socket`. By default the platform-specific default value is used.

`socket` : | a GSocket.
`ttl` : | the time-to-live value for all unicast packets on `socket`

Since 2.32

### g_socket_get_ttl ()

    guint               g_socket_get_ttl                    (GSocket *socket);

Gets the unicast time-to-live setting on `socket`; see `g_socket_set_ttl()` for more details.

`socket` : | a GSocket.
Returns : | the time-to-live setting on `socket`

Since 2.32

### g_socket_get_broadcast ()

    gboolean            g_socket_get_broadcast              (GSocket *socket);

Gets the broadcast setting on `socket`; if `TRUE`, it is possible to send packets to broadcast addresses or receive from broadcast addresses.

`socket` : | a GSocket.
Returns : | the broadcast setting on `socket`

Since 2.32

### g_socket_set_broadcast ()

    void                g_socket_set_broadcast              (GSocket *socket,
                                                             gboolean broadcast);

Sets whether `socket` should allow sending to and receiving from broadcast addresses. This is `FALSE` by default.

`socket` : | a GSocket.
`broadcast` : | whether `socket` should allow sending to and receiving from broadcast addresses

Since 2.32

### g_socket_get_option ()

    gboolean            g_socket_get_option                 (GSocket *socket,
                                                             gint level,
                                                             gint optname,
                                                             gint *value,
                                                             GError **error);

Gets the value of an integer-valued option on `socket`, as with ``getsockopt()``. (If you need to fetch a non-integer-valued option, you will need to call ``getsockopt()`` directly.)

The `<gio/gnetworking.h>` header pulls in system headers that will define most of the standard/portable socket options. For unusual socket protocols or platform-dependent options, you may need to include additional headers.

Note that even for socket options that are a single byte in size, `value` is still a pointer to a gint variable, not a guchar; `g_socket_get_option()` will handle the conversion internally.

`socket` : | a GSocket
`level` : | the "API level" of the option (eg, `SOL_SOCKET`)
`optname` : | the "name" of the option (eg, `SO_BROADCAST`)
`value` : | return location for the option value. [out]
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | success or failure. On failure, `error` will be set, and the system error value (`errno` or ``WSAGetLastError()``) will still be set to the result of the ``getsockopt()`` call.

Since 2.36

### g_socket_set_option ()

    gboolean            g_socket_set_option                 (GSocket *socket,
                                                             gint level,
                                                             gint optname,
                                                             gint value,
                                                             GError **error);

Sets the value of an integer-valued option on `socket`, as with ``setsockopt()``. (If you need to set a non-integer-valued option, you will need to call ``setsockopt()`` directly.)

The `<gio/gnetworking.h>` header pulls in system headers that will define most of the standard/portable socket options. For unusual socket protocols or platform-dependent options, you may need to include additional headers.

`socket` : | a GSocket
`level` : | the "API level" of the option (eg, `SOL_SOCKET`)
`optname` : | the "name" of the option (eg, `SO_BROADCAST`)
`value` : | the value to set the option to
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | success or failure. On failure, `error` will be set, and the system error value (`errno` or ``WSAGetLastError()``) will still be set to the result of the ``setsockopt()`` call.

Since 2.36

### g_socket_get_family ()

    GSocketFamily       g_socket_get_family                 (GSocket *socket);

Gets the socket family of the socket.

`socket` : | a GSocket.
Returns : | a GSocketFamily

Since 2.22

### g_socket_get_fd ()

    int                 g_socket_get_fd                     (GSocket *socket);

Returns the underlying OS socket object. On unix this is a socket file descriptor, and on Windows this is a Winsock2 SOCKET handle. This may be useful for doing platform specific or otherwise unusual operations on the socket.

`socket` : | a GSocket.
Returns : | the file descriptor of the socket.

Since 2.22

### g_socket_get_local_address ()

    GSocketAddress *    g_socket_get_local_address          (GSocket *socket,
                                                             GError **error);

Try to get the local address of a bound socket. This is only useful if the socket has been bound to a local address, either explicitly or implicitly when connecting.

`socket` : | a GSocket.
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | a GSocketAddress or `NULL` on error. Free the returned object with `g_object_unref()`. [transfer full]

Since 2.22

### g_socket_get_protocol ()

    GSocketProtocol     g_socket_get_protocol               (GSocket *socket);

Gets the socket protocol id the socket was created with. In case the protocol is unknown, -1 is returned.

`socket` : | a GSocket.
Returns : | a protocol id, or -1 if unknown

Since 2.22

### g_socket_get_remote_address ()

    GSocketAddress *    g_socket_get_remote_address         (GSocket *socket,
                                                             GError **error);

Try to get the remove address of a connected socket. This is only useful for connection oriented sockets that have been connected.

`socket` : | a GSocket.
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | a GSocketAddress or `NULL` on error. Free the returned object with `g_object_unref()`. [transfer full]

Since 2.22

### g_socket_get_socket_type ()

    GSocketType         g_socket_get_socket_type            (GSocket *socket);

Gets the socket type of the socket.

`socket` : | a GSocket.
Returns : | a GSocketType

Since 2.22

### g_socket_speaks_ipv4 ()

    gboolean            g_socket_speaks_ipv4                (GSocket *socket);

Checks if a socket is capable of speaking IPv4.

IPv4 sockets are capable of speaking IPv4. On some operating systems and under some combinations of circumstances IPv6 sockets are also capable of speaking IPv4. See RFC 3493 section 3.7 for more information.

No other types of sockets are currently considered as being capable of speaking IPv4.

`socket` : | a GSocket
Returns : | `TRUE` if this socket can be used with IPv4.

Since 2.22

### g_socket_get_credentials ()

    GCredentials *      g_socket_get_credentials            (GSocket *socket,
                                                             GError **error);

Returns the credentials of the foreign process connected to this socket, if any (e.g. it is only supported for `G_SOCKET_FAMILY_UNIX` sockets).

If this operation isn't supported on the OS, the method fails with the `G_IO_ERROR_NOT_SUPPORTED` error. On Linux this is implemented by reading the `SO_PEERCRED` option on the underlying socket.

Other ways to obtain credentials from a foreign peer includes the GUnixCredentialsMessage type and `g_unix_connection_send_credentials()` / `g_unix_connection_receive_credentials()` functions.

`socket` : | a GSocket.
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | `NULL` if `error` is set, otherwise a GCredentials object that must be freed with `g_object_unref()`. [transfer full]

Since 2.26

### g_socket_join_multicast_group ()

    gboolean            g_socket_join_multicast_group       (GSocket *socket,
                                                             GInetAddress *group,
                                                             gboolean source_specific,
                                                             const gchar *iface,
                                                             GError **error);

Registers `socket` to receive multicast messages sent to `group`. `socket` must be a `G_SOCKET_TYPE_DATAGRAM` socket, and must have been bound to an appropriate interface and port with `g_socket_bind()`.

If `iface` is `NULL`, the system will automatically pick an interface to bind to based on `group`.

If `source_specific` is `TRUE`, source-specific multicast as defined in RFC 4604 is used. Note that on older platforms this may fail with a `G_IO_ERROR_NOT_SUPPORTED` error.

`socket` : | a GSocket.
`group` : | a GInetAddress specifying the group address to join.
`iface` : | Name of the interface to use, or `NULL`. [allow-none]
`source_specific` : | `TRUE` if source-specific multicast should be used
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | `TRUE` on success, `FALSE` on error.

Since 2.32

### g_socket_leave_multicast_group ()

    gboolean            g_socket_leave_multicast_group      (GSocket *socket,
                                                             GInetAddress *group,
                                                             gboolean source_specific,
                                                             const gchar *iface,
                                                             GError **error);

Removes `socket` from the multicast group defined by `group`, `iface`, and `source_specific` (which must all have the same values they had when you joined the group).

`socket` remains bound to its address and port, and can still receive unicast messages after calling this.

`socket` : | a GSocket.
`group` : | a GInetAddress specifying the group address to leave.
`iface` : | Interface used. [allow-none]
`source_specific` : | `TRUE` if source-specific multicast was used
`error` : | GError for error reporting, or `NULL` to ignore.
Returns : | `TRUE` on success, `FALSE` on error.

Since 2.32

### g_socket_get_multicast_loopback ()

    gboolean            g_socket_get_multicast_loopback     (GSocket *socket);

Gets the multicast loopback setting on `socket`; if `TRUE` (the default), outgoing multicast packets will be looped back to multicast listeners on the same host.

`socket` : | a GSocket.
Returns : | the multicast loopback setting on `socket`

Since 2.32

### g_socket_set_multicast_loopback ()

    void                g_socket_set_multicast_loopback     (GSocket *socket,
                                                             gboolean loopback);

Sets whether outgoing multicast packets will be received by sockets listening on that multicast address on the same host. This is `TRUE` by default.

`socket` : | a GSocket.
`loopback` : | whether `socket` should receive messages sent to its multicast groups from the local host

Since 2.32

### g_socket_get_multicast_ttl ()

    guint               g_socket_get_multicast_ttl          (GSocket *socket);

Gets the multicast time-to-live setting on `socket`; see `g_socket_set_multicast_ttl()` for more details.

`socket` : | a GSocket.
Returns : | the multicast time-to-live setting on `socket`

Since 2.32

### g_socket_set_multicast_ttl ()

    void                g_socket_set_multicast_ttl          (GSocket *socket,
                                                             guint ttl);

Sets the time-to-live for outgoing multicast datagrams on `socket`. By default, this is 1, meaning that multicast packets will not leave the local network.

`socket` : | a GSocket.
`ttl` : | the time-to-live value for all multicast datagrams on `socket`

Since 2.32

## Property Details

### The `"blocking"` property

      "blocking"                 gboolean              : Read / Write

Whether or not I/O on this socket is blocking.

Default value: TRUE

### The `"broadcast"` property

      "broadcast"                gboolean              : Read / Write

Whether the socket should allow sending to and receiving from broadcast addresses.

Default value: FALSE

Since 2.32

### The `"family"` property

      "family"                   GSocketFamily         : Read / Write / Construct Only

The sockets address family.

Default value: G_SOCKET_FAMILY_INVALID

### The `"fd"` property

      "fd"                       gint                  : Read / Write / Construct Only

The sockets file descriptor.

Default value: -1

### The `"keepalive"` property

      "keepalive"                gboolean              : Read / Write

Keep connection alive by sending periodic pings.

Default value: FALSE

### The `"listen-backlog"` property

      "listen-backlog"           gint                  : Read / Write

Outstanding connections in the listen queue.

Allowed values: [0,128]

Default value: 10

### The `"local-address"` property

      "local-address"            GSocketAddress*       : Read

The local address the socket is bound to.

### The `"multicast-loopback"` property

      "multicast-loopback"       gboolean              : Read / Write

Whether outgoing multicast packets loop back to the local host.

Default value: TRUE

Since 2.32

### The `"multicast-ttl"` property

      "multicast-ttl"            guint                 : Read / Write

Time-to-live out outgoing multicast packets

Default value: 1

Since 2.32

### The `"protocol"` property

      "protocol"                 GSocketProtocol       : Read / Write / Construct Only

The id of the protocol to use, or -1 for unknown.

Default value: G_SOCKET_PROTOCOL_UNKNOWN

### The `"remote-address"` property

      "remote-address"           GSocketAddress*       : Read

The remote address the socket is connected to.

### The `"timeout"` property

      "timeout"                  guint                 : Read / Write

The timeout in seconds on socket I/O

Default value: 0

Since 2.26

### The `"ttl"` property

      "ttl"                      guint                 : Read / Write

Time-to-live for outgoing unicast packets

Default value: 0

Since 2.32

### The `"type"` property

      "type"                     GSocketType           : Read / Write / Construct Only

The sockets type.

Default value: G_SOCKET_TYPE_STREAM

## See Also

GInitable, gnetworking.h