NAME
	datagram_challenge - set the datagram challenge

SYNOPSIS
	void datagram_challenge(string challenge)


DESCRIPTION
	Set the datagram challenge for the current binary user object.  The
	client must send this challenge in order to open the datagram channel,
	after which open_datagram() will be called in the object.  All
	outstanding challenges must be unique.

ERRORS
	An error will result if a challenge has already been set for the
	current object.

NOTES
        This kfun is not active when the network extensions are enabled.

SEE ALSO
	kfun/query_ip_name, kfun/query_ip_number, kfun/send_datagram,
	kfun/this_user, kfun/users