Object Hierarchy:

GLib.Socket GLib.Socket GLib.Socket GLib.Object GLib.Object GLib.Object->GLib.Socket GLib.DatagramBased GLib.DatagramBased GLib.DatagramBased->GLib.Socket GLib.Initable GLib.Initable GLib.Initable->GLib.Socket


[ CCode ( type_id = "g_socket_get_type ()" ) ]
[ Version ( since = "2.22" ) ]
public class Socket : Object, DatagramBased, Initable

A Socket 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.

Socket 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 SocketClient , SocketService and SocketConnection. However there may be cases where direct use of Socket is useful.

Socket implements the Initable interface, so if it is manually constructed by e.g. @new you must call init and check the results before using the object. This is done automatically in Socket and Socket.from_fd, so these functions can return null.

Sockets operate in two general modes, blocking or non-blocking. When in blocking mode all operations (which don’t take an explicit blocking parameter) 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 condition_check, or condition_wait. You can also use create_source and attach it to a MainContext 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.

Sockets 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 Socket causes the signal sigpipe to be ignored for the remainder of the program. If you are writing a command-line utility that uses Socket, 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.

Like most other APIs in GLib, Socket is not inherently thread safe. To use a Socket concurrently from multiple threads, you must implement your own locking.

Example: Sockets:

public static void server (SocketAddress address) throws Error {
Socket socket = new Socket (SocketFamily.IPV4, SocketType.STREAM, SocketProtocol.TCP);
assert (socket != null);

socket.bind (address, true);
socket.set_listen_backlog (10);
socket.listen ();

for (int i = 0; true ; i = (i + 1) % 10) {
Socket connection = socket.accept ();
print (@"Accepted ($i)\n");

connection.send (i.to_string ().data);

public static void client (SocketAddress address) throws Error {
Socket socket = new Socket (SocketFamily.IPV4, SocketType.STREAM, SocketProtocol.TCP);
assert (socket != null);

socket.connect (address);
print ("Connected\n");

uint8 buffer[100];
ssize_t len;

len = socket.receive (buffer);
stdout.write (buffer, len);
print ("\n");

public static int main (string[] args) {
try {
if (args.length != 2) {
print ("%s server|client\n", args[0]);
return 0;

InetAddress address = new InetAddress.loopback (SocketFamily.IPV4);
InetSocketAddress inetaddress = new InetSocketAddress (address, 2001);

if (args[1] == "server") {
server (inetaddress);
} else if (args[1] == "client") {
client (inetaddress);
} else {
print ("Unknown option.\n");
} catch (Error e) {
print ("Error: %s\n", e.message);

return 0;

valac --pkg gio-2.0 GLib.Socket.vala

Namespace: GLib
Package: gio-2.0



Creation methods:


Inherited Members:

All known members inherited from interface GLib.Initable