TCP/IP

[luopeng2019]

Hello everyone, how can we achieve two-way communication between TCP/IP client and server? The following figure shows the problem of TCPtest using LabVIEW example test. What is the reason?

[GerdW]

Hi lu,

mind to translate that Chinese error description?

[crossrulz]

Error code 63 means that the connection was refused.  Why?  Well, it could be incorrect settings, a firewall issue, or even the order in which you start the server and client VIs (the server needs to start first).

[rolfk · Accepted solution]

Actually error 63 would not occur if the server hasn't been started. In that case the Open Connection would get an error 56 timeout error. Firewalls could cause that but generally will simply drop all packets without sending back any packets. A firewall does not want to make it easy to an adversery to detect that there is actually anything that actively prevents the connection. Instead it simply acts as one big black hole where everything that its rules say is not right is send to the big void.

Error 63 typically happens when the listen socket in the server did receive the connection request but the server did not accept it or did immediately close it. This could be for a myriad of reasons but it generally has to do with something like that the server expects a certain initial reaction and/or a TSL handshake and if that doesn't happen it simply drops the connection without further ado. It also could be that the server is not prepared to handle multiple connections at the same time and already connected to someone else. The listen socket did receive the request and acknowledge it but the connection was never accepted and after some time discarded by the network socket stack.

[luopeng2019]

Thank you for your answer. Is there any solution? I turned off the firewall and the problem was not resolved.

[rolfk]

There most probably is. But since we can't debug an image, not even if it would be from the diagram rather than just a dialog which for me shows just gibberish instead of text, (sorry but my Chinese is simply non-existent) you will have to do that yourself.

Show us your code that fails, both the server and the client and we might be just able to point out the possible problem to you!