Python TCP client

Question

Hi, I have a WIZ550S2E module, I’m writing a python application that must send data to the serial port over TCP… I tried to write a really simple TCP client, I can connect to the WIZnet TCP server, send data, but I never receive a response, I just get a timeout. Could someone tell me what I am doing wrong ? Thank you ! Here’s a minimal code sample: import socket import time ip, port = '192.168.1.150', 6000 # Open a TCP socket with a 1 second timeout sock = socket.socket() sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1) sock.settimeout(1) # Connection is OK sock.connect((ip, port)) print("Connected to %s:%s" % (ip, port)) # Send the connection password sock.sendall(b"WIZnet") # whatever I send here, I get no response #sock.sendall(b"Hello") # this gives a timeout print(sock.recv(1024)) Running the code: $ python tcpclient.py Connected to 192.168.1.150:6000 Traceback (most recent call last): File "test.py", line 19, in <module> print(sock.recv(1024)) socket.timeout: timed out Here’s a screenshot of the configuration tool: conf-tool848×710 60.4 KB

izimobil · Answer

FWIW, here’s a screenshot of the packets captured by wireshark when I run the sample code: wireshark1264×771 106 KB

izimobil · Answer

Hi Lawrence ! Many thanks for your reply. If I disable the timeout, the script hangs indefinitely on the “sock.recv(1024)” line, meaning that it receives no response from the unit with the WIZ550S2E card. I realize I wasn’t very clear on what I’m trying to achieve. I’m writing a software (running on a PC) that want to send and receive packets over TCP to a serial based software running on a micro-controller with a WIZ550S2E card connected to it’s serial port, so the communication should be bidirectionnal. Here’s a diagram: I attached the wireshark file of the script running with the timeout removed. test.pcapng.zip (721 Octets) Thanks !

izimobil · Answer

Hi again, If it can help, I tried via telnet, and same: I can send data but not receive. Here is a telnet session that closes because I did not sent the password in 5 seconds (normal): $ telnet 192.168.1.150 6000 Trying 192.168.1.150... Connected to 192.168.1.150. Escape character is '^]'. Connection closed by foreign host. And one that stays up because I sent the password (note that there’s no response): $ telnet 192.168.1.150 6000 Trying 192.168.1.150... Connected to 192.168.1.150. Escape character is '^]'. WIZnet +++ Attached the wireshark file for the second telnet session. telnet.pcapng.zip (797 Octets) Thanks.

lawrence · Answer

Hi, Thank you for more detiails! First, I would like to check what you have done for tcp loopback. I put the picture for explaining WIZ550S2E normal operation and what customer have to do for loopback. Basically. WIZ550S2E only bypass tcp data to serial data. And… that’s it. If re-send the received data from serial, mcu must control WIZ550s2e to send the data with send command. image1071×542 23.9 KB Could you check how the red part you have done? thank you

lawrence · Answer

If you are looking for the loopback example, here is the link. github.com ioLibrary_Driver/Application/loopback at master · Wiznet/ioLibrary_Driver master/Application/loopback ioLibrary_Driver can be used for the application design of WIZnet TCP/IP chips as W5500, W5300, W5200, W5100 W5100S. hope it will be helpful