line_server.py

buffer = b''                      # This is the partial line buffer.
while 1:
    buffer += socket.recv(1024)   # Read up to 1024 bytes and append it to the buffer.
    lines = buffer.split(b'\n')   # Split the buffer by newlines.
    buffer = lines[-1]            # The last piece is a partial line.
    for line in lines[:-1]:       # Every other piece is a complete line.
        process(line)