第十一章：网络通信-socket:网络通信-UNIX域套接字_unix域套接字和tcp的区别

11.2.4 UNIX域套接字
从程序员的角度来看，使用UNIX域套接字和TCP/IP套接字村长两个根本区别。首先，套接字的地址是文件系统上的一个路径，而不是一个包含服务器名和端口的元组。其次，文件系统中创建的表示套接字的节点会持久保存，即使套接字关闭也仍然存在，所以每次服务器启动时都需要将其删除。只需在设置部分做一些修改，就可以把前面的回送服务器例子更新为使用UDS。
需要基于地址簇AF_Unix创建socket。套接字的绑定和入站连接的管理与对TCP/IP套接字的做法相同。

import socket
import sys
import os

server_address = './uds_socket'

# Make sure the socket does not already exist.
try:
    os.unlink(server_address)
except OSError:
    if os.path.exists(server_address):
        raise

# Create a UDS socket.
sock = socket.socket(socket.AF_UNIX,socket.SOCK_STREAM)

# Bind the socket to the address.
print('starting up on {}'.format(server_address))
sock.bind(server_address)

# Listen for incoming connections.
sock.listen(1)

while True:
    # Wait for a connection.
    print('waiting for a connection')
    connection,client_address = sock.accept()
    try:
        print('connection from',client_address)

        # Receive the data in small chunks and retransmit it.
        while True:
            data = connection.recv(16)
            print('received {!r}'.format(data))
            if data:
                print('sending data back to the client')
                connection.sendall(data)
            else:
                print('no data from',client_address)
                break
    finally:
        # Clean up the connection.
        connection.close()
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还需要修改客户设置以使用UDS。要假设套接字的相应文件系统节点存在，因为服务器要通过绑定这个地址创建套接字。UDS客户中发送和接收数据的做法与前面的TCP/IP客户是一样的。

import socket
import sys

# Create a UDS socket.
sock = socket.socket(socket.AF_UNIX,socket.SOCK_STREAM)

# Connect the socket to the port where the server is listening.
server_address = './uds_socket'
print('connecting to {}'.format(server_address))
try:
    sock.connect(server_address)
except socket.error as msg:
    print(msg)
    sys.exit(1)

try:
    # Send data.
    message = b'This is the message. It will be repeated.'
    print('sending {!r}'.format(message))
    sock.sendall(message)

    amount_received = 0
    amount_expected = len(message)

    while amount_received < amount_expected:
        data = sock.recv(16)
        amount_received += len(data)
        print('received {!r}'.format(data))
finally:
    print('closing socket')
    sock.close()
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程序输出基本上相同，但对地址信息有适当的更新。服务器显示接收的消息和发回给客户的消息。

客户立即发送所有消息，并采用增量方式逐个部分地接收消息。