python achieve nc

#!/usr/bin/python2
import sys
import socket
import getopt
import thread
import subprocess


listen              =False
command             =False
upload              =False
execute             =""
target              =""
upload_destination  =""
port                =0


def usage():
    print("hello netcat!")
    sys.exit(0)


# 作为客户端使用，接受与发送信息
def client_sender():
    buffer=""
    client=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
    try:
        client.connect((target,port))
        while True:
            recv_len =1
            response =""

            while recv_len:
                data=client.recv(4096)
                recv_len=len(data)
                response+=data

                
                if recv_len < 4096:
                    break
            if "#" in response:
                print(response),
                buffer = raw_input("")
                buffer += "\n"
                client.send(buffer)
            else:
                print(response)

    except:
        print("connection failed!")
        client.close()


#作为服务器端使用
def server_loop():
    global target
    if not len(target):
        target="0.0.0.0"

    server=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
    server.bind((target,port))
    server.listen(5)
    print("listening!!!!!")
    while True:
        try:
            client_socket,addr=server.accept()
            print("accepting!!!!")
            #创建一个新线程处理连接到本服务器的客户端
            thread.start_new_thread(client_handler,(client_socket,))
        except:
            print("thread fail")
            break


#将客户端传来的信息转换为命令执行，并输出执行结果到output
def run_command(command):
    command=command.rstrip()
    try:
        output=subprocess.check_output(command,stderr=subprocess.STDOUT,shell=True)
    except:
        output="failed to execute command.\r\n"
    return output


#处理连接到本服务器的客户端
def client_handler(client_socket):
    global upload
    global execute
    global command

    print("goto handler")
    #如果客户端传来要上传文件的路径
    if len(upload_destination):
        file_buffer = ""
        while True:
            data = client_socket.recv(1024)

            if not data:
                break
            else:
                file_buffer+=data

        try:
        #写入传来的文件
            file_descriptor=open(upload_destination,"wb")
            file_descriptor.write(file_buffer)
            file_descriptor.close()

            client_socket.send("successfully saved")
        except:
            client_socket.send("failed to save")
    #执行一条传来的命令
    if len(execute):
        output=run_command(execute)
        client_socket.send(output)

   #交互式执行传来的命令，shell面板
    if command:
         while True:
             client_socket.send("<netcat: #> ")

       
             cmd_buffer=""
             while "\n" not in cmd_buffer:
                 cmd_buffer+=client_socket.recv(1024)

             response=run_command(cmd_buffer)
             client_socket.send(response)


def main():
    global listen
    global port
    global execute
    global command
    global upload_destination
    global target
    global opts

    if not len(sys.argv[1:]):
        usage()

    try:
        opts,args=getopt.getopt(sys.argv[1:],"hle:t:p:cu",["help","listen","execute","target","port","command","upload"])
    except:
        usage()

    for o,a in opts:
        if o in ("-h","--help"):
            usage()
        elif o in ("-l","--listen"):
            listen=True
        elif o in ("-e","--execute"):
            execute=a
        elif o in ("-c","--commandshell"):
            command=True
        elif o in ("-u","--upload"):
            upload_destination=a
        elif o in ("-t","--target"):
            target=a
        elif o in ("-p","--port"):
            port=int(a)

    if not listen and len(target) and port>0:
    
        client_sender()

    if listen:
        server_loop()
main()

Client client:

   client_sender()     发送接受信息

Server server:

server_loop function to listen and call a new thread execution client_handler () function

Client_Handler () function
1.upload_destination client to file transfer server

2.command including run_command () function, the client information transmitted becomes command and save the result in the output
Server output sent to client