Experimental Physics and
Industrial Control System

tcp        0      0 IP...37:5064   0.0.0.0:*      LISTEN      29499/MAG-CYSI
tcp    86888 178656 IP...37:5064   IP...41:40147  ESTABLISHED 29499/MAG-CYSI

On the archiver VM (...41), we see

tcp   495144  70184 IP...41:40147  IP...37:5064   ESTABLISHED 9164/java
tcp        0      0 IP...41:40691  IP...49:5064   ESTABLISHED 9164/java

tcpdump shows no traffic on that connection.

The archive engine logs things like:

2017-06-12 22:17:53.047 WARNING [Thread 30] com.cosylab.epics.caj.impl.CATransport (noSyncSend) - Failed to send message to /IP...37:5064 - buffer full, will retry.

and has not written data to the archive from this IOC for a long time. It is happily archiving data from other connections (e.g. the one shown in line 2 of the netstat output above).

Obviously the TCP connection is blocked and backed up to the other host in both directions.

The IOC is alive and casr shows all channels as connected.

Why are both sides not taking data out of their receive-Qs?

In this test setup, this is not happening to us for the first time. Has anyone seen such situations before? Any ideas for how to proceed trying to find out what's happening?

Thanks a lot
~Ralph