XDMCP
| application | XDMCP | ||||
| transport | UDP | ||||
| Internet | IP ( IPv4 , IPv6 ) | ||||
| Network access | Ethernet |
Token bus |
Token ring |
FDDI | ... |
XDMCP ( X D isplay M anager C ontrol P rotocol ) is a network protocol used for communication between an X server and an X display manager . The requesting X server usually runs on an X terminal to which a logon service is to be made available.
functionality
The X Display Manager acts as a server in the XDMCP. It waits on UDP port 177 for requests of the type QUERY(single request ) and BROADCAST_QUERY(a broadcast request that was not directed to an X server, but goes to an entire subnet ). If he receives such a request, he can WILLINGrespond with a packet. This contains information about the server, but it does not oblige the client to establish the connection.
The chooser
A chooser usually provides a list of available display managers. This can be a list of predefined hosts with their respective networkBROADCAST_QUERY addresses or a list that was obtained through an email request. Most of the time, the host itself is also listed as it provides a display manager.
If the user selects a host from the list, the X server on the local computer connects to the X display manager on the remote computer.