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I am looking at possible issues with TCPIP port sharing for a server application written in C. The documentation indicates that the application does not have to do anything as the port sharing is transparent to the server and client applications.

The client / server application is working fine with the port sharing TCPIP setup (3 servers running all using the same port) with no source code changes. The concern is if we change something in our application it could stop the port sharing from working.

Is there anything that should be avoided in the way the applications sets up the connection? Is there anything else we should be aware of?

Michael Taylor
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1 Answers1

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Port Sharing is pretty simple to setup for any z/OS server and should be transparent to the application, as long as there are no issues about shared state. If you want port sharing to work effectively the key issues are connection persistence and overload.

  • If connections are persistent for an extended period of time it can be hard to rebalance work across the servers if a server comes back online, so consider how to timeout.
  • If the system is overloaded, you may want to consider how you handle additional connection requests (i.e do you reject or delay). Delaying the accept() processing has the benefit that the backlog queue for that listeners socket will grow and thus drive negative feedback into the metrics used by port sharing.
Ben Cox
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Phil Wakelin
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