Troubleshooting IBM i Dispatcher (YOBSYTCP/YOBSYTCPDP) Errors

Document ID : KB000027666
Last Modified Date : 14/02/2018
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Listed below are common errors that might occur when running a Plex application that connects through the Plex dispatcher on an IBM i machine. All of the errors below can be found in the QPRINT log file generated on the IBM i machine. This log file is located in either the OUTQ of the user profile that submits the dispatcher program, or in the OUTQ of the connecting user profile.


  1. Error on socket bind: errorno = 3420.

    The error 3420 means the port is already in use.

    Conditions that may cause this error include:

    • the port specified was not available, in use or blocked by a firewall

    • the TCP/IP or QINTER subsystem is not running

    If this error is encountered, change the port number to use an available port or if the incoming port is blocked by a firewall, use the alternate YOBSYTCPDP dispatcher. (YOBSYTCP does not operate through a firewall.)

  2. Error on read of pinfo: errno = 3426

    This error occurs when there is an abrupt disconnection between the PC and the IBM i.

    Possible causes of the problem include:

    • user has logged off the PC without first ending the Plex application

    • user has powered off the PC without first ending Plex application

    • network outage

  3. Error on connect to client socket: errno = 3447

    Error 3447 means the host did not respond within the timeout period.

    Possible causes of the problem:

    • a period of inactivity between the PC and the IBM i caused connection to terminate

      Verify the keepalive value in the IBM i CHGTCPA command is set to an appropriate value. The keepalive parameter is a value specifying the interval at which the IBM i communicates over the connection to keep the connection from timing out.