Tcpclient send [FIN, ACK]

Hi!

I'm trying to communicate with an external server from MATLAB using tcpclient.

To test the connection, the server can be quarried with a ping sending a message in the format '{ "Ping" : 1 }', the response is '{ "Pong" : 1 }'.

Using wireshark, a correct sequence for the ping procedure is:

i.e. the server expects a tcp packet with the FIN flag enabled indicating "end of message" .

Using python the behavior can be replicated using the socket library

import socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(('localhost', 8333))

s.sendall('{ "Ping" : 1 }'.encode())
s.shutdown(1)
data = s.recv(15)
print ('Received', data.decode())

Using Matlab and tcpclient I'm not able to get this behavior with the FIN packets, indicating end of message.

I've tried

client = tcpclient("0.0.0.0",8333,'Timeout',1)
configureTerminator(client,"CR")

data='{ "Ping" : 1 }'
writeline(client,data)

response=readline(client)

fclose(client);
delete(client)

but the server only response after getting a [FIN] packet, which only occurs with "delete(client)", which means I cannot handle the response as I've just deleted the client.

My question is if there's a way to sending a [FIN] packet without deleting the object handling the communication using tcpclient and Matlab?

Kind regards

/Marcus

Answer 1

[Mathy]

Hi Malin,

You can make use to Python MATLAB interface to resolve the issue.

Here is the sample code,

s = py.socket.socket(py.socket.AF_INET, py.socket.SOCK_STREAM)
s.connect({'localhost', int32(8333)});
req = py.str('{ "Ping" : 1 }').encode()
s.sendall(req);
s.shutdown(1);
data = s.recv(15)

For this to work, you need MATLAB compatible python installed in your system. You can check the python compatible versions here:

https://www.mathworks.com/support/requirements/python-compatibility.html

Hope this helps!