TCP Read returns no error and zero bytes

[endeavor]

Mark,

I do like Wireshark but the problem is that unfortunately I have no direct access to the PC where this issue occurs. I've also never seen such weirdness with TCP primitives before...

[Mark_Yedinak]

Can you trace at the sender or are you running this on an RT system? I have a very nice passive tap that is used for sniffing networks that allows you to put a trace anywhere one the network (you do require physical access). However this is not a cheap piece of hardware. You could also try to dig up a network hub (not a switch) and connect that where you do have access. Then simply connect your laptop or PC there to sniff the network.

Beyond this I don't have much else to offer you. You definitely have encountered something strange.

[PhillipBrooks]

Couple of thoughts, ideas. Could any type of antivirus app be filtering/modifying the data? Might you have the error in to your tcp read wired to your case selector (passes under the tcp read node) instead of the error out? That might explain no error combined with no data.

[endeavor]

Mark,

the program is running on a PC. Unfortunately any 'hardware debugging' is not possible at the moment just because the customers are quite far and not ready to involve their specialists into solving this issue. So I'm still hoping for solving it remotely.

Thanks a lot for your suggestions.

[endeavor]

Hi Phillip,

many thanks for your suggestions. The code is clean, everything is connected correctly. As far as I know they do not use antivirus but I'll check again (not sure it could cause such strange behaviour, however).

[MarcoMauri]

Do you confirm that the problem is happening only sometimes?

Is the connection used elsewhere in the code?

I do not undestand if when the problem occours TCP Read waits for the whole 5s.

Regards,

Marco

[endeavor]

Yep, only sometimes, I would say several times per day (the system is running 24/7).

The connection is using in a sequential "request—response" way. Still had no chance to check your ideas on waiting time and a warning, I hope to be able to make it tomorrow.

[GregFreeman]

I have had strange issues as is shown here with a TCP write functioning fine with no error, then the read timing out. I know it's not the exact same thing, but, do you have multiple connections that could be causing some strange issue? Just shooting in the dark on this one.

[Mark_Yedinak]

Is this running on a Win 7 machine?

[endeavor]

Hi Greg,

thanks for the shooting! No multiple connections unfortunately.