TCP/IP Connection closing

[Paul Brown_2]

We are running Symbol Spectrum 24 terminals on a 9000 series server, accessing an application.

The radio terminals 'bomb out' and display a message "Connection closed by Foreign host".

Analysis so far has eliminated the network as a factor.

Analysis of traffic has shown the terminal sending an acknowledgement of a screen update to the host, with no subsequent traffic from the host.

It also shows the host sending 0 byte packets to the terminal, as if a pseudo terminal slave is trying to communicate with a master. The connection closing also fits in with a pseudo terminal master being closed and a SIGHUP message terminating the tty.

Has anyone else experienced this, what would cause the master to close during processing, and is there a remedy?

[rick jones]

in your packet traces, do you see TCP segments with the FIN bit set, or with the RST bit set? if the FIN bit is set from the host, it implies that the application initiated the close, not the TCP stack.

if the RST bit is set in the segment, it implies that the TCP stack initiated the close - an abort actually - either it was trying to zero-window probe, or perhaps TCP keepalive probes that never generated a response from the terminal