Identifying Unique Connections

In a network, RSCS may need to communicate with more than one NJE node. In this case, RSCS must differentiate where each link driver is connected. For physical links, the subchannel address identifies each unique connection. For TCP/IP sockets, however, the local and remote IP address and port numbers uniquely identify the connection. Port numbers are global within the same IP address.

Each TCPNJE link driver must listen on a specific port (which is defined to the other NJE node by the RMTPORT parameter) and the IP address of the remote node must be defined to the link. The TCPNJE link driver must also define a local port number (using the LCLPORT parameter); this port is used to listen for CONNECT requests from the remote NJE node. If the local and remote NJE nodes are on different systems, the default values for the RMTPORT and LCLPORT parameters can be used to define the links. See z/VM: RSCS Networking Planning and Configuration for more information about other TCPNJE link parameters.

For each TCPNJE-type link, one IUCV connection is used between RSCS and the TCP/IP virtual machine.