The current documentation for GSocketService's incoming signal notes:

The ::incoming signal is emitted when a new incoming connection to service needs to be handled. The handler must initiate the handling of connection, but may not block; in essence, asynchronous operations must be used. 

Need to update this to reflect the fact that the user needs to do g_object_ref() to do anything meaningful with this connection (e.g. send/receive data) from a different thread. Currently as soon as the signal handler returns, the connection gets dropped.