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Appendix E. TCP/IP Application Exit Points and Programs
Certain TCP/IP applications provide exit points that enable them to call
customer-written exit programs. This appendix contains the following information:
v Conceptual information on TCP/IP exit points and programs
v General instructions on creating exit programs for TCP/IP applications
v Descriptions of the TCP/IP application exit point interfaces
v Specific instructions on how to prepare exit programs for each TCP/IP application
exit point, with examples.
TCP/IP Exit Points and Exit Programs
An exit point is a specific point in the TCP/IP application program where control
may be passed to an exit program. An exit program is a program to which the exit
point passes control.
For each exit point, there is an associated programming interface, called an exit
point interface. The exit point uses this interface to pass information between the
TCP/IP application and the exit program. Each exit point has a unique name. Each
exit point interface has an exit point format name that defines how information is
passed between the TCP/IP application and the customer-written exit program.
Different exit points may share the same exit point interface. When this is the case,
multiple exit points can call a single exit program.
Figure 293 shows how parameters and control are passed from the TCP/IP
application program to the customer-written exit program and back again.
OS/400 Registration Facility
Exit points for TCP/IP applications are automatically registered when the parent
product or option is installed, using the OS/400 registration facility. The
registration facility contains a repository that allows customers to associate their exit
programs with specific exit points. TCP/IP applications check the registration facility
repository to determine which exit program to call for a particular exit point.
AS/400 TCP/IP Application
┌───────────────────┐ Exit Point Customer
│ │ Interface Exit Program
│ │ 1 │ │ ┌──────────┐
│ Application ───>│ Parameters │───────>│ │
│ Exit │ │ │ 2 │
│ Point <─────│ Return Code│<───────│ │
│ 4 │ │ Returned │ 3 └──────────┘
│ │ │ Values │
└───────────────────┘
Processing flow:
1 TCP/IP application passes request parameters to the exit program
2 Exit program processes request parameters
3 Exit program returns information to the TCP/IP application
4 TCP/IP application performs operation based on exit program response.
Figure 293. TCP/IP Exit Point Processing
© Copyright IBM Corp. 1997, 1999 535