Hi,

Our application is using jeromq 0.4.3 within java process and communicates with zeromq within cpp process.
We implemented push/pull method through 2 sockets.

First socket: CPP is server and Java is client.
Second socket: Java is server and CPP is client.

It has been working fine for over 50 days and now the problem appeared in 4 different servers running this setup, after approximately same period of running. Our sockets are under load of a couple of thousand messages per second.

When looking through netstat (we are using RHEL OS), we can see that socket status is ESTABLISHED (both of them), but when collecting tcpdump, we can see that there is no tcp messages on second socket.

In our code, we can see that this condition is statisfied:
sender.send(jsonInString, ZMQ.DONTWAIT) == false

Client restart didn't resolve this issue. The issue was resolved only after server restart, but this is not a valid solution if software is used by customers.

What would be the possible reason for socket communication not working even though OS says that socket is established.

Kind regards,
M