攻克python3-socket

socket

socket通常也称作"套接字"，用于描述IP地址和端口，是一个通信链的句柄，应用程序通常通过"套接字"向网络发出请求或者应答网络请求。

sk.bind(address)

　　s.bind(address) 将套接字绑定到地址。address地址的格式取决于地址族。在AF_INET下，以元组（host,port）的形式表示地址。

sk.listen(backlog)

　　开始监听传入连接。backlog指定在拒绝连接之前，可以挂起的最大连接数量。

      backlog等于5，表示内核已经接到了连接请求，但服务器还没有调用accept进行处理的连接个数最大为5
      这个值不能无限大，因为要在内核中维护连接队列

sk.setblocking(bool)

　　是否阻塞（默认True），如果设置False，那么accept和recv时一旦无数据，则报错。

sk.accept()

　　接受连接并返回（conn,address）,其中conn是新的套接字对象，可以用来接收和发送数据。address是连接客户端的地址。

　　接收TCP 客户的连接（阻塞式）等待连接的到来

sk.connect(address)

　　连接到address处的套接字。一般，address的格式为元组（hostname,port）,如果连接出错，返回socket.error错误。

sk.connect_ex(address)

　　同上，只不过会有返回值，连接成功时返回 0 ，连接失败时候返回编码，例如：10061

sk.close()

　　关闭套接字

sk.recv(bufsize[,flag])

　　接受套接字的数据。数据以字符串形式返回，bufsize指定最多可以接收的数量。flag提供有关消息的其他信息，通常可以忽略。

sk.recvfrom(bufsize[.flag])

　　与recv()类似，但返回值是（data,address）。其中data是包含接收数据的字符串，address是发送数据的套接字地址。

sk.send(string[,flag])

　　将string中的数据发送到连接的套接字。返回值是要发送的字节数量，该数量可能小于string的字节大小。即：可能未将指定内容全部发送。

sk.sendall(string[,flag])

　　将string中的数据发送到连接的套接字，但在返回之前会尝试发送所有数据。成功返回None，失败则抛出异常。

      内部通过递归调用send，将所有内容发送出去。

sk.sendto(string[,flag],address)

　　将数据发送到套接字，address是形式为（ipaddr，port）的元组，指定远程地址。返回值是发送的字节数。该函数主要用于UDP协议。

sk.settimeout(timeout)

　　设置套接字操作的超时期，timeout是一个浮点数，单位是秒。值为None表示没有超时期。一般，超时期应该在刚创建套接字时设置，因为它们可能用于连接的操作（如 client 连接最多等待5s ）

sk.getpeername()

　　返回连接套接字的远程地址。返回值通常是元组（ipaddr,port）。

sk.getsockname()

　　返回套接字自己的地址。通常是一个元组(ipaddr,port)

sk.fileno()

　　套接字的文件描述符

import socket
 
server = socket.socket()  # 生成socket句柄
# server = socket.socket(AF.INET, sock_STREAM)
server.bind(('localhost', 6960))  # 绑定监控的端口
server.listen(5)  # 监听绑定的端口
print('waitting...')
 
conn, addr = server.accept()  # 等待客户端连接
print(conn, addr)
 
while True:
    data = conn.recv(1024)  # 接收客户端数据 
    print('recv:', data.decode())
    conn.send(data)  # 向客户端发送数据
 
conn.close()

import socket
 
client = socket.socket()  # 生成socket句柄
client.connect(('localhost', 9999))  # 链接服务器端
 
while True:
    msg = input('>>').strip()
    if msg == 0: continue
 
    client.send(msg.encode('utf-8'))  # 向服务器端发送数据
    data = client.recv(1024)
    print('recv:', data.decode())  # 接收服务器端数据
 
client.close()

存在的问题

1.客户端断开时，服务器端也会自动断开报错。

解决方法：a.添加异常处理机制。

　　　　    b.服务器端判断接受到的字符串是否为空(客户端断开后，会继续发送空字符)。

　　　　    c.服务器使用socketserver。

2.可能存在的粘包问题(send函数发送数据，有一种机制会当发送的数据达到缓存区大小时或等待缓冲区超时，再统一发送，而不是send一次发送一次)。

解决方法：a.每发送一个文件，接受方收到后返回一个确实收到值，避免连续发送。

　　　　　b.发送文件前，先将文件大小发送给接收方，使接受方只接收相应大小的数据。

实现简单的ssh

import socket,os


#实例化socket
ser=socket.socket()
#绑定ip与端口
ser.bind(('localhost',9999))
#监听
ser.listen()
while True:
    #阻塞，等待链接
    print("开始等！")
    conn,addr=ser.accept()
    while True:
        #接受命令
        try:
            data=conn.recv(1024)
            #执行命令返回字符
            print("开始执行命令！")
            cmd_res=os.popen(data.decode()).read()
            if len(cmd_res)==0:
                cmd_res="命令错误"
            #发送字符长度
            conn.send(str(len(cmd_res.encode("utf-8"))).encode("utf-8"))
            #接受回应，防止粘包
            conn.recv(1024)
            #发送命令结果
            conn.send(cmd_res.encode("utf-8"))
            print("发送完成！")
        except Exception as e:
            print(e)
            break

import socket

#声明socket对象
cli=socket.socket()
#链接
cli.connect(("localhost",9999))
while True:
    #输入命令
    cmd=input(">>:")
    #传送命令
    cli.send(cmd.encode("utf-8"))
    data_size=int(cli.recv(1024).decode())
    cli.send(b"200")
    recv_data=b""
    recv_size=0
    #循环接受数据直到收完
    while data_size>recv_size:
        #防止粘包
        if data_size-recv_size<1024:
            size=data_size-recv_size
        else:
            size=1024
        #接受数据
        data=cli.recv(size)
        recv_size+=len(data)
        recv_data+=data
    else:
        print(recv_data.decode())

socketserver

为了实现服务器端多连接的问题，封装的socketserver模块。

The socketserver module simplifies the task of writing network servers.

There are four basic concrete server classes:

class socketserver.TCPServer(server_address, RequestHandlerClass, bind_and_activate=True)

This uses the Internet TCP protocol, which provides for continuous streams of data between the client and server. If bind_and_activate is true, the constructor automatically attempts to invoke server_bind() andserver_activate(). The other parameters are passed to the BaseServer base class.

class socketserver.UDPServer(server_address, RequestHandlerClass, bind_and_activate=True)

This uses datagrams, which are discrete packets of information that may arrive out of order or be lost while in transit. The parameters are the same as for TCPServer.

class socketserver.UnixStreamServer(server_address, RequestHandlerClass, bind_and_activate=True)

class socketserver.UnixDatagramServer(server_address, RequestHandlerClass,bind_and_activate=True)

These more infrequently used classes are similar to the TCP and UDP classes, but use Unix domain sockets; they’re not available on non-Unix platforms. The parameters are the same as for TCPServer.

These four classes process requests synchronously; each request must be completed before the next request can be started. This isn’t suitable if each request takes a long time to complete, because it requires a lot of computation, or because it returns a lot of data which the client is slow to process. The solution is to create a separate process or thread to handle each request; the ForkingMixIn and ThreadingMixIn mix-in classes can be used to support asynchronous behaviour.

There are five classes in an inheritance diagram, four of which represent synchronous servers of four types:

+------------+
| BaseServer |
+------------+
      |
      v
+-----------+        +------------------+
| TCPServer |------->| UnixStreamServer |
+-----------+        +------------------+
      |
      v
+-----------+        +--------------------+
| UDPServer |------->| UnixDatagramServer |
+-----------+        +--------------------+

Note that UnixDatagramServer derives from UDPServer, not from UnixStreamServer — the only difference between an IP and a Unix stream server is the address family, which is simply repeated in both Unix server classes.

class socketserver.ForkingMixIn

class socketserver.ThreadingMixIn

Forking and threading versions of each type of server can be created using these mix-in classes. For instance, ThreadingUDPServer is created as follows:

class ThreadingUDPServer(ThreadingMixIn, UDPServer):
    pass

The mix-in class comes first, since it overrides a method defined in UDPServer. Setting the various attributes also changes the behavior of the underlying server mechanism.

class socketserver.ForkingTCPServer

class socketserver.ForkingUDPServer

class socketserver.ThreadingTCPServer

class socketserver.ThreadingUDPServer

These classes are pre-defined using the mix-in classes.

Request Handler Objects

class socketserver.BaseRequestHandler

This is the superclass of all request handler objects. It defines the interface, given below. A concrete request handler subclass must define a new handle() method, and can override any of the other methods. A new instance of the subclass is created for each request.

setup()

Called before the handle() method to perform any initialization actions required. The default implementation does nothing.

handle()

This function must do all the work required to service a request. The default implementation does nothing. Several instance attributes are available to it; the request is available as self.request; the client address as self.client_address; and the server instance as self.server, in case it needs access to per-server information.

The type of self.request is different for datagram or stream services. For stream services,self.request is a socket object; for datagram services, self.request is a pair of string and socket.

finish()

Called after the handle() method to perform any clean-up actions required. The default implementation does nothing. If setup() raises an exception, this function will not be called.

 利用socketserver实现ssh客服端

import socketserver

class MyTCPHandler(socketserver.BaseRequestHandler):
    def handle(self):
        while True:
            try:
                self.data = self.request.recv(1024).strip()
                print("{} wrote:".format(self.client_address[0]))
                print(self.data)
                self.request.send(self.data.upper())
            except ConnectionResetError as e:
                print("err",e)
                break
if __name__ == "__main__":
    HOST, PORT = "localhost", 9999
    # Create the server, binding to localhost on port 9999
    server = socketserver.ThreadingTCPServer((HOST, PORT), MyTCPHandler)
    server.serve_forever()