Use a TCPIPSVR.DAT file on the client.
In order to have an application running on a client machine point to a specific server, place a file named TCPIPSVR.DAT in the \Windows\System32 directory. TCPIPSVR.DAT should be a standard ASCII text file (such as those created by Notepad) and should contain one line with either the full IP address or network name of the server. The placement of the file is architecture dependent. 64-bit OS require placement of this file in either \sysWOW64 or \system32 depending upon the architecture of the application.
You can also use the install utility to create a TCPIPSVR.DAT file. When you install the client software, click the Set Server button. The utility will then allow you to either enter a network name or IP address manually or select the desired dongle server from a list of dongle servers currently active on the network.