TCP server in local network stays busy forever

I'm trying to build a TCP connection between two PCs in my local network. The code for the server looks like this:

   tcp_server = tcpip('192.168.xxx.yyy', 30000, 'NetworkRole', 'server');
   tcp_server.BytesAvailableFcnMode = 'terminator';
   tcp_server.Terminator = 19;
   fopen(tcp_server);

The code for my client looks like this:

    tcp_client = tcpip('192.168.xxx.yyy', 30000, 'NetworkRole', 'client');
    fopen(tcp_client);
    fwrite(tcp_client,'hello world');

When I start the code on localhost (using 127.0.0.1 as IP adress) it has no problem working. The instance of MATLAB that's running stays busy until the client connects and then I can begin sending packages back and forth.

When using this same code on the local network between different machines though, the MATLAB instance running the server just stays busy, even after the client has connected. It's like it just freezes up.

I know for sure that the TCP over the network works, because I can connect two PC via TCP using the same network adresses using some C# code that I wrote. So the problem defenetly lies in MATLAB. Also connecting my C# server on one computer to a MATLAB client on another works flawlessly. It's just MATLAB server getting stuck in "Busy" when trying to connect via Network.

Answer 1

[sen sun]

i am faced with similar problem,have you solved you problem? i will appreciate that you can give me some idea or advice.

[Sami Al-Khayat]

Hi, sadly i never ended finding a solution, just a workaround. I was writing two pieces of software for the client and server. One is written in C#, the other in MATLAB. So my workaround was to simply switch the roles. I made the C# application my server and MATLAB the client. It's not the best solution, especially because it made the workflow with those two applications a bit more complicated, but it works for my case.

[Sami Al-Khayat]

I'd still love to find an actual solution though, so if anybody reading this knows what I'm doing wrong, please leave a comment!

[sen sun]

maybe firewall is the keypoint.close firewall when using tcp/ip.

[Sami Al-Khayat]

I've tried this before with no sucess, on different machines and different networks as well.

You mentioned that your problem is similar. What problem do you have, maybe we can come up with a solution that works for us both if we're stuck on a similar problem.

Answer 2

[sen sun]

firewall(status:open) lead to communication failure.when i close firewall,they run successfully,can send and receive date correctly. i copy your code,and run on my computer.they run successfully

 tcp_s = tcpip('0.0.0.0', 30000, 'NetworkRole', 'server');
 tcp_s.BytesAvailableFcnMode = 'terminator';
 tcp_s.Terminator = 19;
 fopen(tcp_s);

 tcp_c = tcpip('localhost', 30000, 'NetworkRole', 'client');
 fopen(tcp_c);
 fwrite(tcp_c,'hello world');

Answer 3

[sen sun]

even using two computers,each one run server or client code,they can communicate successfully. tcp_s = tcpip('0.0.0.0', 30000, 'NetworkRole', 'server'); tcp_s.BytesAvailableFcnMode = 'terminator'; tcp_s.Terminator = 19; fopen(tcp_s); tcp_c = tcpip('IPV4 address',30000,'NetworkRole','client'); fopen(tcp_c); fwrite(tcp_c,'hello world');

[Sami Al-Khayat]

I just tried that again. I closed firewall on both machines and tried connecting my C# client to my MATLAB server, both running basically the code above. No sucess, MATLAB stays busy forever, eventhough my C# client seems to be connected to the server. And as before when I create a C# server and connect a MALAB Client it works perfectly fine.