python3 tcp自定制报头

发送时：
先发报头长度(dict->json.dumps序列号(json字符串)->bytes->struct.pack打包)
再编码报头内容然后发送(dict->json字符串->bytes)
最后发真实内容

接收时：
先接收报头长度，用struct取出来(struct.unpack解包)
根据取出的长度收取报头内容，然后解码，反序列化(解码->json.loads反序列化->dict)
从反序列化的结果中取出待取数据的描述信息，然后去取真实的数据内容

--------------------------------------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)  # 数据的长度
    headers = {"data_size": cmd_result_len}  # 报头信息(dict类型)
    header_json = json.dumps(headers)  # 报头信息(json字符串)
    header_json_bytes = bytes(header_json, encoding="utf-8")  # 报头信息(bytes类型)

    conn.send(struct.pack('i', len(header_json_bytes)))  # 先发送报头的长度
    conn.send(header_json_bytes)  # 再发送报头的内容
    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)  # 先接收报头的长度(bytes类型)
    from_server_head_msg_len = struct.unpack('i', from_server_head_msg_len)  # 解包(tuple类型)
    print("来自服务端的消息:", from_server_head_msg_len[0])  # 元组的第一个元素为报头的长度
    from_server_head_msg = client.recv(from_server_head_msg_len[0])  # 接收报头信息
    from_server_head_msg = from_server_head_msg.decode("utf-8")  # 报头信息解码
    from_server_head_msg = json.loads(from_server_head_msg)  # 报头信息转化为dict类型
    print("来自服务端的消息:", from_server_head_msg)
    from_server_real_msg = client.recv(1024)  # 接收真正的数据
    from_server_real_len = len(from_server_real_msg)  # 获取一次接收数据的大小
    while from_server_head_msg['data_size'] > from_server_real_len:  # 判断数据是否接收完整
        from_server_real_msg += client.recv(1024)  # 再次接收没接收完的数据
        from_server_real_len = len(from_server_real_msg)  # 再次统计已接收数据的大小

    print("来自服务端的消息:", from_server_real_msg.decode("gbk"))

client.close()