python3 tcp custom header

When sending: 
first transmitter header length (dict-> json.dumps sequence number (JSON string) -> bytes-> struct.pack packing) 
re-encoded header and the content transmission (dict-> json string -> bytes) 
last sent the true content 

is received: 
received first header length, taken out with a struct (struct.unpack unpacked) 
charged content based on the length of the header removed, then decoded, deserialization ( decoding -> json.loads deserialization -> dict ) 
from deserialized extracted result of access to data information to be described, then the contents of the real data fetch

--------------------------------------tcp_server.py--------------------------------------
# coding:utf-8
import json
import struct
import socket
import subprocess

server = socket.socket()
ip_port = ("127.0.0.1", 8001)
server.bind(ip_port)
server.listen(5)

while 1:
    conn, addr = server.accept()
    from_client_msg = conn.recv(1024)
    if not from_client_msg.decode("utf-8"):
        break
    print("来自客户端的消息:", from_client_msg.decode("utf-8"))
    res = subprocess.Popen(
        from_client_msg.decode("utf-8"),
        shell=True,
        stdout=subprocess.PIPE,
        stderr=subprocess.PIPE,
    )
    cmd_result = res.stderr.read()
    if not cmd_result:
        cmd_result =res.stdout.read () 
    cmd_result_len = len (cmd_result)   # data length 
    headers = { " Data_Size " : cmd_result_len}   # header information (dict type) 
    header_json = json.dumps (headers)   # header information (JSON string) 
    header_json_bytes bytes = (header_json, encoding = " UTF-. 8 " )   # header information (bytes type) 

    conn.send (struct.pack ( ' I ' , len (header_json_bytes)))   # sends the length of the header 
    conn.send (header_json_bytes)   # and then send the header content 
    conn.sendall (cmd_result)   # 最后发送数据

conn.close()
server.close()


--------------------------------------tcp_client.py--------------------------------------
# coding:utf-8
import json
import struct
import socket

client = socket.socket()
ip_port = ("127.0.0.1", 8001)
client.connect(ip_port)

while 1:
    cmd = input(">>>: ").strip()
    if not cmd: continue
    client.send(cmd.encode(" UTF-. 8 " )) 
    from_server_head_msg_len = client.recv (. 4)   # received first header length (bytes Type) 
    from_server_head_msg_len struct.unpack = ( ' I ' , from_server_head_msg_len)   # unpack (tuple type) 
    Print ( " from the service side message: " , from_server_head_msg_len [0])   # the first element of the tuple is the length of the header 
    from_server_head_msg = client.recv (from_server_head_msg_len [0])   # receiving header information 
    from_server_head_msg = from_server_head_msg.decode ( " UTF-. 8 " )   # header decoding information
    = json.loads from_server_head_msg (from_server_head_msg)   # header information into a type dict 
    Print ( " message from the service side: " , from_server_head_msg) 
    from_server_real_msg = client.recv (1024)   # receiving actual data 
    from_server_real_len = len (from_server_real_msg)   # Get a received size of the data 
    the while from_server_head_msg [ ' Data_Size ' ]> from_server_real_len:   # judging whether the data reception complete 
        from_server_real_msg + = client.recv (1024)   # again not received data completely received 
        from_server_real_len = len (from_server_real_msg)   # statistical data size received again

    Print ( " message from the service side: " , from_server_real_msg.decode ( " GBK " )) 

client.close ()