When you issue a connection establishment request using an RPC or the TCP/IP communication facility, TP1/Client/J enables you to specify the transmission source host for the CUP. This is called the source host specification facility.

If multiple network adapters are connected on the host where the CUP is running, the transmission source host to be used by the CUP when connection establishment is requested is determined by TCP/IP control. However, if you use the source host specification facility, you can fix the transmission source host to be used when the following connection establishment requests are issued:

• RPC using the scheduler direct facility
• RPC using the name service
• RPC using the remote API facility
• RPC specifying the communication destination
• TCP/IP communication facility

To specify the transmission source host for a CUP, use the dccltcupsndhost operand in the TP1/Client/J environment definition.

The following figure shows connection establishment when the source host specification facility is not used and when it is used.

Figure 2-38 When the source host specification facility is not used and when the facility is used