Can't connect to a python socket

Question

I am trying to send a string from STM32H750B-DK with TCP and receive and print it in python. Here is C code for TCP server:

/*
 * tcpserver.c
 *
 * Created on: Apr 20, 2022
 * Author: controllerstech.com
 */
#include "lwip/opt.h"
#include "lwip/api.h"
#include "lwip/sys.h"
#include "tcpserver.h"
#include "string.h"
static struct netconn *conn, *newconn;
static struct netbuf *buf;
static ip_addr_t *addr;
static unsigned short port;
char msg[100];
char smsg[200];
char b[10] = {'0'};
/**** Send RESPONSE every time the client sends some data ******/
static void tcp_thread(void *arg)
{
 err_t err, accept_err, recv_error;
 /* Create a new connection identifier. */
 conn = netconn_new(NETCONN_TCP);
 if (conn!=NULL)
 {
 /* Bind connection to the port number 7. */
 err = netconn_bind(conn, IP_ADDR_ANY, 146);
 if (err == ERR_OK)
 {
 /* Tell connection to go into listening mode. */
 netconn_listen(conn);
 while (1)
 {
 /* Grab new connection. */
 accept_err = netconn_accept(conn, &newconn);
 /* Process the new connection. */
 if (accept_err == ERR_OK)
 {
 /* receive the data from the client */
 while (netconn_recv(newconn, &buf) == ERR_OK)
 {
 /* Extrct the address and port in case they are required */
 addr = netbuf_fromaddr(buf); // get the address of the client
 port = netbuf_fromport(buf); // get the Port of the client
 /* If there is some data remaining to be sent, the following process will continue */
 do
 {
 strncpy (msg, buf->p->payload, buf->p->len); // get the message from the client
 if (msg[0]==103){
 b[0] = '1';
 }
 else{
 b[0] = 'h';
 }
 // Or modify the message received, so that we can send it back to the client
 int len = sprintf (smsg, "\"%s\" was sent by the Server\n", b);
 netconn_write(newconn, smsg, len, NETCONN_COPY); // send the message back to the client
 memset (msg, '0円', 100); // clear the buffer
 }
 while (netbuf_next(buf) >0);
 netbuf_delete(buf);
 }
 /* Close connection and discard connection identifier. */
 netconn_close(newconn);
 netconn_delete(newconn);
 }
 }
 }
 else
 {
 netconn_delete(conn);
 }
 }
}
void tcpserver_init(void)
{
 sys_thread_new("tcp_thread", tcp_thread, NULL, DEFAULT_THREAD_STACKSIZE,osPriorityNormal);
}

And here is python code for TCP client I am using:

import socket
SERVER_IP = "0.0.0.0"
SERVER_PORT = 146
# Create a socket
server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_socket.bind((SERVER_IP, SERVER_PORT))
server_socket.listen(1)
print("Server listening on", SERVER_IP, "port", SERVER_PORT)
while True:
 client_socket, client_address = server_socket.accept()
 print("Connection from:", client_address)
 data = client_socket.recv(1024)
 if data:
 received_variable = int(data.decode())
 print("Received variable:", received_variable)
 client_socket.close()

When IP address is set to 0.0.0.0 it should listen on all available network interfaces so the program works, in console I get the message "Server listening on 0.0.0.0 port 146", but can't get the connection. When I set the IP to 169.254.211.100 (IP address of my STM32) I get this error:

line 43, in <module>
 server_socket.bind((SERVER_IP, SERVER_PORT))
OSError: [WinError 10049] The requested address is not valid in its context

Otherwise I tried receiving the string in hercules and had no trouble connecting and receiving the string so I don-t understand why this doesn't work.

• Martin Scheuchenpflug: If you use socket.bind in Python too, you are creating a second tcp server. You have to use socket.connect. Take a look at: stackoverflow.com/questions/32445310/…
• Steffen Ullrich: socket.listen + socket.accept creates a TCP server, not a TCP client. So you are basically have implement two server which wait for some client to connect - but no client. Use socket.connect instead with the IP and port of STM32 as destination. socket.bind is usually not needed for the client at all since a local IP address and port for the connection will be picked automatically when connecting.
• AK16: Thanks. I don't know how I missed that. It works fine now.