Names and locations of camera servers

This page is part of the ING document INS-DAS-24: client-server interface for control of cameras

Camera servers are named after the cameras they operate: examples are EEV13 and WHTWFC. The names are always in upper case: the case is significant to DRAMA. If a client specifies the server name in the wrong case, then it will not be able to see the server.

The servers run on the DAS computer, while the clients are typically on the system-coordinate computer. DRAMA networking is used to link the two machines. The IMP network agents must be active on both computers before the clients and servers can communicate. Furthermore, the network agents on each machine must be using the same IP port-number. By convention, the port-number is 50001 for the JKT, 50002 for the INT and 50004 for the WHT (i.e. the last digit is the size of the mirror in metres!).

To make a network connection to a new server-programme, a client must qualify the name with the IP address: examples are EEV13@lpss14.roque.ing.iac.es and WHTWFC@crater.roque.ing.iac.es. It is safer to give the full IP name, even though the system may be able to infer the name of the domain. It should not be necessary to use IP numbers.

Most clients do not need to qualify the server name with the address, and should not do so. The IP address of the DAS computer may change, and there may be more than one DAS computer at a telescope (the WHT is intended to use two as a matter of course). Hence, clients must not hard-code the addresses. Instead, the start-up script for the central intelligence on the system computer will determine the addresses of the required camera servers, and will make first contact with these servers. Once one client has contacted a server, then all other clients can see a proxy for that server locally, on the system computer. Clients can then use the unqualified name to talk to the server.