python 网络编程——客户端

网络通信的基本接口是socket，它扩展了操作系统的基本I/O到网络网络通信。socket可以通过socket()函数来建立，通过connect()函数来连接。得到了socket，可以确定本地和远程端点的IP地址和端口号。socket对不同的协议来说都是一种通用的接口，它可以处理TCP和UDP通信。

建立socket需要两步：建立socket对象、连接到远程服务器上

import socket
print "Creating socket"
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)  #指明通信类型和协议家族
print "Done!"

print "Connecting to remote host..."
s.connect(("www.baidu.com", 80))
print "Done"

运行结果

Creating socket
Done!
Connecting to remote host...
Done

查找端口号

通过协议名和端口名查找端口号（unix系统可以在etc/services中找到对应的端口号）

import socket
print "Creating socket"
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print "Done!"

print "Looking up port number..."
port = socket.getservbyname("http", "tcp")
print port
print "done!"

print "Connecting to remote host..."
s.connect(("www.baidu.com", port))
print "Done!!"

运行结果

Creating socket
Done!
Looking up port number...
80
done!
Connecting to remote host...
Done!!

从socket获得信息

import socket
print "Creating socket"
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print "Done!"

print "Looking up port number..."
port = socket.getservbyname("http", "tcp")
print port
print "done!"

print "Connecting to remote host..."
s.connect(("www.baidu.com", port))
print "Done!!"

print "Connected from", s.getsockname()  #获得本地机器的ip和端口号（端口号由操作系统随机分配，每次都不一样）
print "Connected to", s.getpeername()    #获得连接机器的ip和端口号

一次运行结果

Creating socket
Done!
Looking up port number...
80
done!
Connecting to remote host...
Done!!
Connected from ('192.168.209.129', 56245)
Connected to ('220.181.112.244', 80)

利用socket通信

socket对象：send()、sendto()、recv()、recvfrom()

文件类对象：read()、write()、readline()

处理错误

import socket, sys

host = sys.argv[1]
textport = sys.argv[2]
filename = sys.argv[3]

try:
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
except socket.error, e:
    print "Strange error creating socket: %s" % e
    sys.exit(1)

try:
    port = int(textport)
except ValueError:
    try:
        port = socket.getservbyname(textport, 'tcp')
    except socket.error, e:
        print "Couldn't find your port: %s" % e
        sys.exit(1)

try:
    s.connect((host, port))
except socket.gaierror, e:
    print "Address-related error connecting to server: %s" %e
    sys.exit(1)
except socket.error, e:
    print "Connection error: %s" %e
    sys.exit(1)

try:
    s.sendall("GET %s HTTP/1.0\r\n\r\n" % filename)
except socket.error, e:
    print "Error sending data: %s" %e
    sys.exit(1)
print "---------------------------------------"

while 1:
    try:
        buf = s.recv(2048)
    except socket.error, e:
        print "========Error receving data: %s=======" %e
        sys.exit(1)
    if not len(buf):
        break
    sys.stdout.write(buf)
print "---------------------------------------"

改进

#coding: utf-8
import socket
import sys
import time

host = sys.argv[1]
textport = sys.argv[2]
filename = sys.argv[3]

try:
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
except socket.error, e:
    print "Strange error creating socket: %s" % e
    sys.exit(1)

try:
    port = int(textport)
except ValueError:
    print "ValueError"
    try:
        port = socket.getservbyname(textport, 'tcp')
    except socket.error, e:
        print "Couldn't find your port: %s" % e
        sys.exit(1)

try:
    s.connect((host, port))
except socket.gaierror, e:   #主机名不对
    print "Address-related error connecting to server: %s" %e
    sys.exit(1)
except socket.error, e:      #连接远程主机有问题
    print "Connection error: %s" %e
    sys.exit(1)

print "Sleepping........."
time.sleep(10)
print "Continuing."

try:
    s.sendall("GET %s HTTP/1.0\r\n\r\n" % filename)
except socket.error, e:
    print "Error sending data: %s" % e
    sys.exit(1)

try: 
    s.shutdown(1)
except socket.error, e:
    print "Error sending data (detected by shutdown):%s" % e
    sys.exit(1)
    

print "---------------------------------------"
while 1:
    try:
        buf = s.recv(2048)
        print "try"
    except socket.error, e:
        print "========Error receving data: %s=======" %e
        sys.exit(1)

    if not len(buf):  #接受的为空
        print "breaK"
        break
    sys.stdout.write(buf)
print "---------------------------------------"