Together with Gtk.Plug, Gtk.Socket provides the ability to embed widgets from one process into another process in a fashion that is transparent to the user. One process creates a Gtk.Socket widget and, passes the window ID of that widget to the other process, which then creates a Gtk.Plug with that window ID. Any widgets contained in the Gtk.Plug then will appear inside the first applications window.

The window ID of the Gtk.Socket is obtained by using Socket.GetId(). Before using this function, the socket must have been realized, and therefore, have been added to its parent.

Gtk.Socket socket = new Gtk.Socket;
socket.Show ();
parent.Add (socket);
Console.WriteLine ("The ID of the sockets window is {0}", socket.Id);
        

Note that if you pass the window ID of the socket to another process that will create a plug in the socket, you must make sure that the socket widget is not destroyed until that plug is created. Violating this rule will cause unpredictable consequences, the most likely consequence being that the plug will appear as a separate toplevel window. You can check if the plug has been created by examining the plug_window field of the Gtk.Socket structure. If this field is non-null, then the plug has been successfully created inside of the socket.

When Gtk# is notified that the embedded window has been destroyed, then it will destroy the socket as well. You should always, therefore, be prepared for your sockets to be destroyed at any time when the main event loop is running.

The communication between a Gtk.Socket and a Gtk.Plug follows the XEmbed protocol. This protocol has also been implemented in other toolkits, e.g. Qt, allowing the same level of integration when embedding a Qt widget in GTK or vice versa.

A socket can also be used to swallow arbitrary pre-existing top-level windows using Socket.Steal(), though the integration when this is done will not be as close as between a Gtk.Plug and a Gtk.Socket.