When loading the network manager on Intel-based UNIX machines two copies of tcpmgr are started. The second copy is used only when operating as a combined client-server. This second copy is not present on non-Intel machines.
The UNIX TCP network manager is a process that forks. As each client establishes a TCP connection a separate copy of tcpmgr is launched to service that client connection. At any time the number of copies running will be the number of active client connections plus two on Intel based machines or plus one on non-Intel machines.
Most other aspects of DP4 networking on Unix and Linux are very different between releases up to 4.523, and releases from 4.525, and so they are documented separately.