python unix socket_unix domain socket 浅析

unix domain socket

unix domain socket 是在socket架构上发展起来的用于同一台主机的进程间通讯(IPC: Inter-Process Communication),它不需要经过网络协议栈,不需要打包拆包、计算校验和、维护序号和应答等,只是将应用层数据从一个进程拷贝到另一个进程。UNIX Domain Socket有SOCK_DGRAM或SOCK_STREAM两种工作模式,类似于UDP和TCP,但是面向消息的UNIX Domain Socket也是可靠的,消息既不会丢失也不会顺序错乱。

UNIX Domain Socket可用于两个没有亲缘关系的进程,是全双工的,是目前使用最广泛的IPC机制,比如X Window服务器和GUI程序之间就是通过UNIX Domain Socket通讯的。

UNIX Domain socket与网络socket类似,可以与网络socket对比应用。

上述二者编程的不同如下:

address family为AF_UNIX

因为应用于IPC,所以UNIXDomain socket不需要IP和端口,取而代之的是文件路径来表示“网络地址”。这点体现在下面两个方面。

地址格式不同,UNIXDomain socket用结构体sockaddr_un表示,是一个socket类型的文件在文件系统中的路径,这个socket文件由bind()调用创建,如果调用bind()时该文件已存在,则bind()错误返回。

UNIX Domain Socket客户端一般要显式调用bind函数,而不象网络socket一样依赖系统自动分配的地址。客户端bind的socket文件名可以包含客户端的pid,这样服务器就可以区分不同的客户端。

下面用python代码演示uds的使用

Python代码演示

服务端

#!/usr/bin/env python

# -*- coding: utf-8 -*-

"""

Created on 12/11/17 11:55 AM

@author: Chen Liang

@function: socket_echo_server_uds

"""

import sys

reload(sys)

sys.setdefaultencoding('utf-8')

import socket

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()

客户端

#!/usr/bin/env python

# -*- coding: utf-8 -*-

"""

Created on 12/11/17 11:55 AM

@author: Chen Liang

@function: socket_echo_client_uds

"""

import sys

reload(sys)

sys.setdefaultencoding('utf-8')

import socket

import sys

# Create a UDS socket

sock = socket.socket(family=socket.AF_UNIX, type=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()

客户端一次发送,服务端分批返回。

服务端输出结果如下

root@ubuntu:~/PycharmProjects/python_scripts# python socket_echo_server_uds.py

starting up on ./uds_socket

waiting for a connection

('connection from', '')

received 'This is the mess'

sending data back to the client

received 'age. It will be'

sending data back to the client

received ' repeated.'

sending data back to the client

received ''

('no data from', '')

waiting for a connection

客户端输出结果如下

root@ubuntu:~/PycharmProjects/python_scripts# python socket_echo_client_uds.py

connecting to ./uds_socket

sending 'This is the message. It will be repeated.'

received 'This is the mess'

received 'age. It will be'

received ' repeated.'

closing socket

查看套接字文件的类型如下

root@ubuntu:~/PycharmProjects/python_scripts# ls -l ./uds_socket

srwxr-xr-x 1 root root 0 Dec 11 13:45 ./uds_socket

可见uds文件是socket类型。具体的linux文件类型有以下几种:

Linux的文件类型有以下几种:

文件类型

ls -l显示

普通文件

-

目录

d

符号链接

l

字符设备

c

块设备

b

套接字

s

命名管道

p

参考:

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