On PC TN3270 simulator (MOCHA/PCOM/Rumbha or any other tool’s) we provide the IP address and Port number. In general we provide the port number of TN3270E running on the system.

The system tries to connect to the mainframe in few steps like local pc to mainframe via lan/your company intranet/ internet/cust intranet/cust mainframe tcpip to port 23 or if connected through VDI/CITRIX to customer envi. pc to lan/intranet/mainframe tcpip – then to port 23.

The workstation client (tn3270) connects to TCP/IPand to TN3270E (server running on the Mainframe and application that communicate with vtam.). Then the TN3270E server allocates VTAM resources and establishes a logical session on behalf of the connecting client.

TN3270 based on its setup and ACB creates an LU(Minor node) in VTAM under the TN3270E Majnode defined. The BEGINVTAM section of the profile dataset has DEFAULTLU’s statement that provide the range for the MINORNODE to establish the pcom session.

The USSTCP parameter in the BEGINVTAM section points to a table. This table has the statements that would give the first banner and what needs to happen when we give the logon applid(xxxx) or xxxx on the first page. This table is a module needs in the steplib used for TN3270/VTAM/TCPIP.