doc/concepts/imp

CONCEPT
        imp

LAST UPDATED
        Deepthought, 10-Nov-92
        Pepel,             18-Nov-93

DESRIPTION
        This document describes IMP, the intermud message protocol,
        also known as Intermud-1.

        Imp messages are exchanged between muds using UDP
        (unreliable datagram protocol) packets. Each mud provides
        a connection endpoint which is given by the ip host address
        and the UDP port number. Muds may then send messages to
        this port by using the efun send_udp(). The applied function
        receive_udp will be called by the driver in the master
        object if a imp message arrives at the mud's UDP port.

        Imp message packets have the following format:

        password@objectname@functionname[[@argument]...]

        <password> is the connection password to verify incoming
        imp packets. It is encoded using crypt(E) and compared to
        the stored password. Each mud participating in the imp
        network has a secret password which is encoded by the
        admin and distributed to remote muds with which the mud
        should have direct connection. Encryted passwords may also
        propagated to other muds over already secure channels.

        <objectname> is a logical name which is not to be confused
        with mudlib object filenames. It is used by receive_msg in
        the master object to route the message to another object by
        associating the logical object name with a real mudlib file
        name. A good idea would be to reserve a special directory
        for imp objects, e.g. /secure/net/<objectname>.

        <functionname> is the function which is called by the master
        object in the object described by <objectname>.

        <argument> are additional arguments which are handed to the
        function <functionname>. The exact definition of functions
        and arguments are left to the imp applications.

AUTHOR
        originally Deepthought

NOTE
        The above is only particularly correct nowadays. Recently a
        package name ``inetd'' was published, that is based on the IMP
        mechanism in the driver (send_udp() and receive_udp()), but
        it uses a different message format. That package seems to
        enjoy much publicity and is installed in a number of muds. For
        details look into the inetd description.

        An other method of inter mud connection is the Mudlink
        package, which uses a normal user connection that is connected
        to a special user object, and an auxiliary process that does
        the connection to other muds.

SEE ALSO
        send_udp(E), receive_udp(M), intermud(C)