IBM Support

Connecting to a remote host with Remote Systems Explorer (RSE) hangs or times out

Troubleshooting


Problem

When using IBM Rational Developer for Power Systems Software (RDP) 8.5 or Rational Developer for System z (RDz) version 8.5 and trying to connect to a remote host, it might take a very long time or fail with a time-out or TCP/IP configuration error message. A message indicating that the host could not be found might also be indicative of this problem.

Cause

When trying to connect from a workstation that is set to have an IPv6 preference through an IPv4 network (such as VPN), it may cause the connection to take a very long time to establish or it may fail and give an error message. This is due to name resolution failing when there is no IPv6 DNS server.

Environment

This is most commonly observed on Microsoft Windows 7 64 bit

Diagnosing The Problem

If the problem is seen when connecting to an IBM i or IBM z operating system, then first ensure that the IP name or address for the host is correct. Then confirm that the host can be reached (ping) and that the appropriate firewall ports are open to enable the RSE connection. Once you confirm this, then the problem will be at the client side if it is due to IPv6.

When connecting to an AIX operating system it could be either client (PC) or host (AIX). To determine if the problem is at the host side start a simple SSH or Telnet console session with the host. Then change the current directory to the RDP install directory on AIX (such as, "cd /opt/IBM/RDPower/8.5/rse/"). Now run the server script ("./server.sh"). If this takes a long time to respond, about two minutes, then the problem exists at the host side.

Resolving The Problem

Client side

To resolve the problem on the client side and cause the RDP or RDz client to use IPv4, add the parameter "-Djava.net.preferIPv4Stack=true" on a new line at the bottom of the eclipse.ini file in the product install directory. This will set the set the network preference to be IPv4 for the product only.

If changing the preference for Windows 7 to be IPv4 is desired then this discussion provides some additional guidance:

Win7 seems to prefer IPv4 native to IPv6/6to4 - which is not what the policy table says - which is right?

AIX host side

To resolve the problem on the AIX host side add the parameter "-Djava.net.preferIPv4Stack=true" to the $javaExe invocations in the runserver.sh script in the RDP install directory on the AIX host.

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Document Information

Modified date:
27 October 2020

UID

swg21610148