NAME
	listen - open a network port and listen for connections

SYNOPSIS
	none listen(num[, obj, protocol])

DESCRIPTION
	This builtin is only functional if LPMOO has been built with
	networking support and the mport_listening configuration option
	is enabled. Otherwise, E_PERM will be returned.

	An attempt is made to open the TCP network port specified by
	`num' on the host machine. If successful, connections received
	on the port will be bound to the object `obj', which must be
	valid. If not specified, `obj' defaults to #0.

	If the port could not be opened because it is already open,
	E_INVARG is returned. If the port could not be opened for other
	reasons (such as resource limitations on the host machine),
	E_QUOTA is returned.

	When a connection is established, obj:do_login_command() will
	be called for received lines of input, per the normal MOO login
	mechanism.

	The port will remain open until it is closed with unlisten(),
	or until the server is shutdown.

	If the argument `protocol' is specified, it must be one of the
	two strings "binary" or "telnet". If not specified, it will
	default to "binary".

	Note that if mport_listening is enabled at all, the normal
	telnet and binary ports will not be opened automatically.
	Therefore at least one call to listen() is required for the
	server to accept any connections. For example, from the
	#0:server_started verb:

		status = dgd_status();
		listen(status[23], #0, "telnet");
		listen(status[24], #0, "binary");

	is equivalent to running LPMOO without mport_listening enabled.

	This builtin requires wizard permissions.

SEE ALSO
	open_network_connection, unlisten, dgd_status