Hey there, let's tackle this WinError 10057 issue you're hitting with your client-server setup. I’ve seen this exact problem a bunch of times, so let’s break down what’s going on and how to fix it.

First, let's decode the core of that error message:

"[WinError 10057] 由于套接字未连接，且（在数据报套接字上使用sendto调用发送时）未提供地址，因此不允许发送或接收数据的请求"

This error almost always boils down to one of two scenarios: you're using a UDP (datagram) socket incorrectly, or your TCP socket hasn't properly established a connection before trying to send/receive data. Let's go through each case:

Scenario 1: You're using UDP sockets (datagram sockets) #

UDP is connectionless, meaning there’s no persistent "link" between client and server. If your server thinks it’s sending messages but nothing gets through, and your client throws this error, here’s what’s wrong:

• The server is probably using send() instead of sendto() — UDP requires you to specify the target client’s IP and port every time you send data, since there’s no pre-established connection.
• The client might be using recv() instead of recvfrom(), or hasn’t sent any initial data to let the server know its address (so the server has nowhere to send messages to).

Fixes for UDP: #

• On the server side, always use sendto(data, (client_ip, client_port)) to send messages. To get the client’s address, first receive a message from the client with data, client_addr = server_socket.recvfrom(buffer_size), then reuse that client_addr for replies.
• On the client side, use recvfrom(buffer_size) to receive data (this gives you both the message and the server’s address), and make sure you send an initial message to the server first so it knows where to send responses.

Here's a quick working UDP example:

Server Code

import socket

# Create UDP socket
server_sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
server_sock.bind(("0.0.0.0", 12345))

# First, get client's address by receiving a message
msg, client_addr = server_sock.recvfrom(1024)
print(f"Got message from client: {msg.decode()}")

# Now send a reply to that address
server_sock.sendto(b"Hey client, I got your message!", client_addr)
server_sock.close()

Client Code

import socket

# Create UDP socket
client_sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

# Send initial message to server (so server knows our address)
client_sock.sendto(b"Hello server!", ("127.0.0.1", 12345))

# Receive server's reply
msg, server_addr = client_sock.recvfrom(1024)
print(f"Got reply from server: {msg.decode()}")
client_sock.close()

Scenario 2: You're using TCP sockets but messed up the connection flow #

TCP is connection-oriented, so you need to properly establish a connection before sending data. If your server has no errors but messages aren’t going through, chances are:

• The server is trying to send data using the listening socket (the one you called bind() and listen() on) instead of the new socket returned by accept(). The listening socket only accepts new connections — it can’t send or receive data.
• The client hasn’t successfully called connect() to establish a connection with the server before trying to receive/send data.

Fixes for TCP: #

• On the server side, after calling listen(), wait for a connection with client_sock, client_addr = server_sock.accept(), then use client_sock to send/receive data.
• On the client side, make sure connect((server_ip, server_port)) completes successfully before any send/recv calls.

Working TCP example:

Server Code

import socket

# Create TCP socket
server_sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_sock.bind(("0.0.0.0", 12345))
server_sock.listen(1)

# Wait for client to connect
client_sock, client_addr = server_sock.accept()
print(f"Connected to {client_addr}")

# Send message via the connected client socket
client_sock.send(b"Welcome to the server!")

client_sock.close()
server_sock.close()

Client Code

import socket

# Create TCP socket
client_sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
# Establish connection to server
client_sock.connect(("127.0.0.1", 12345))

# Receive message from server
msg = client_sock.recv(1024)
print(f"Got message from server: {msg.decode()}")

client_sock.close()

Quick Checklist to Debug: #

• Double-check if you're using TCP or UDP — their workflows are completely different, don't mix them up.
• For UDP: Did you use sendto()/recvfrom() and share addresses between client/server?
• For TCP: Did you use the socket from accept() (server) and call connect() (client) before sending data?
• Verify that both client and server are targeting the correct IP and port (no typos here!).

That should get your client-server communication up and running. Let me know if you need to tweak any part of this for your specific code!

内容的提问来源于stack exchange，提问作者amirhosein majidi