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5.2 Connection Servers

An alternative form of session startup is supported where the local scheduler instance does not spawn the remote instance itself but instead contacts a server running on the corresponding machine which spawns the instance. Such a server is started on the remote machine by invoking typically

java dist.Scheduler server port command

This scheduler instance runs in mode "server" and listens on machine port port for connection requests from the local scheduler (if port is 0, any free port is used). The server responds to such a request by forking the program denoted by command (typically "java start.Scheduler").

For security reasons, the server is protected by a password that the user has to interactively type in when she starts the server and that the local scheduler has to provide when it requests a connection (the password is read from dist.systems).

A typical invocation of the server thus is

java dist.Scheduler server 9966 "java dist.Scheduler"
mypasswd

The server responds by printing the port that it uses (9966) and subsequently runs in a forever loop waiting for connection requests.

Please note that the use of the connection server is a potential security hazard. Any user on the Internet that knows the password of the connection server can contact the server and get on the corresponding machine all privileges of the account under which this server is running.