Every client node has a default server specified in an initialization file, piclient.ini, which is usually located in the PI data directory.
If no server is specified on startup, then the default server is used. The default server is set with the piut_setdefaultservernode function which updates the .ini files as well as sets the current server.
To change the current server or to connect to a new server the piut_setservernode function is specified. If a program is connecting to multiple server nodes, this call must be made before addressing any particular node. This call does not incur any significant overhead when switching to previously established server connections.