socket编程模拟linux下的ssh代码实现

实现思路：

1.提供输入指令的客户端；

2.提供返回执行指令结果的服务端

3.寻找服务端返回结果一次无法全部接收的解决思路

服务端代码（ssh_server.py）

 #coding=utf-8
 import socket,os

 server = socket.socket()
 server.bind(('localhost', 9999))
 server.listen()
 client,addr = server.accept()
 while True:
     data = client.recv(1024)
     if data == '' or data == None:continue
     cmd_res = os.popen(data.decode()).read()
     if len(cmd_res) == 0:
         cmd_res = '指令无效，请重新输入'
     client.send(str(len(cmd_res.encode('utf-8'))).encode('utf-8'))
     client.recv(1024)#更改后
     client.send(cmd_res.encode('utf-8'))
     print(len(cmd_res))
 server.close()

客户端代码（ssh_client.py）

 # coding = utf-8
 import socket

 client = socket.socket()
 client.connect(('localhost',9999))
 while True:
     cmd = input('>>:').strip()
     if len(cmd) == 0:continue
     client.send(cmd.encode('utf-8'))
     data_size = int(client.recv(1024).decode())
     print(data_size)    #字节大小
     curr_size = 0
     final_res = b''
     while data_size != curr_size:
         data = client.recv(1024)
         curr_size += len(data)
         print(curr_size)
         final_res+=data
     print(final_res.decode())

潜在问题：

由于服务器两次发送的数据间歇时间太短，容易造成粘包（服务器发送出的两条信息同时到缓存中，缓存区未满或未超时时内部机制是知道缓存区满才将消息拿出来，多次发送的信息资料由于此种机制的制约
很容易造成粘包，解决思路a.服务器两次发送信息中间加一个是时间间隙，time.sleep(2);b.服务端发出上一条信息后客户端接受到消息后向服务器返回一个标识，服务端接受到该标识后再发送第二波消息）
改进后代码（ssh_server.py）:

#coding=utf-8
import socket,os

server = socket.socket()
server.bind(('localhost', 9999))
server.listen()
client,addr = server.accept()
while True:
    data = client.recv(1024)
    if data == '' or data == None:continue
    cmd_res = os.popen(data.decode()).read()
    if len(cmd_res) == 0:
        cmd_res = '指令无效，请重新输入'
    client.send(str(len(cmd_res.encode('utf-8'))).encode('utf-8'))
    client.recv(1024)#b方式更改后
    client.send(cmd_res.encode('utf-8'))
    print(len(cmd_res))
server.close()

改进后代码（ssh_client.py）

# coding = utf-8
import socket

client = socket.socket()
client.connect(('localhost',9999))
while True:
    cmd = input('>>:').strip()
    if len(cmd) == 0:continue
    client.send(cmd.encode('utf-8'))
    data_size = int(client.recv(1024).decode())
    client.send("received the message...")#b方式更改后
    print(data_size)    #字节大小
    curr_size = 0
    final_res = b''
    while data_size != curr_size:
        data = client.recv(1024)
        curr_size += len(data)
        print(curr_size)
        final_res+=data
    print(final_res.decode())