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How to Create a TCP Client/Server Connection

The socket standard module provides a low-level interface for creating TCP and UDP connections. To create servers with a higher level interface, see the standard socketserver module. For medium and large projects, consider more complete solutions such as Twisted.

Now, to create a TCP connection we need two files: one for the server and one for the client. The server must create a socket object and indicate that it will listen for requests on a given IP address (local or public) and port.

# server.py

from socket import socket

# Create the socket.
with socket() as s:
    # Associate it with an IP address and a port.
    s.bind(("localhost", 6190))
    # Indicate that this socket will act as a server.
    s.listen()
    # Wait for the client to connect.
    print("Waiting for client...")
    conn, address = s.accept()
    print(f"{address[0]}:{address[1]} has connected.")
    # Wait for the client to send data.
    while True:
        data = conn.recv(1024)
        # Check that it is not empty.
        if data:
            # Print received data and close the socket.
            print("The client sent:", data)
            break

# The socket is automatically closed upon exiting the "with" block.
print("Connection closed.")

Once the server is running, we must create and run the client. We are using the create_connection() function to connect to the server and send data over the connection.

# client.py

from socket import create_connection

# Connect to the server.
with create_connection(("localhost", 6190)) as conn:
    print("Connected to server.")
    # Send data.
    conn.sendall(b"Hello world!")

print("Connection closed.")

Both points of the connection can send and receive data via the sendall() and recv(n) methods (where n indicates the size of the buffer in bytes, usually 1024).

See also our article on sending files through a socket.

socket tcp

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