import struct
import json

ver = 1
body = json.dumps(dict(hello="world"))
print(body) # {"hello": "world"}
cmd = 101
header = [ver, body.__len__(), cmd]
headPack = struct.pack("!3I", *header)
print(headPack) # b'\x00\x00\x00\x01\x00\x00\x00\x12\x00\x00\x00e'

# Python Version:3.5.1
import socket
import struct

HOST = ''
PORT = 1234

dataBuffer = bytes()
headerSize = 12

sn = 0
def dataHandle(headPack, body):
  global sn
  sn += 1
  print("第%s個數據包" % sn)
  print("ver:%s, bodySize:%s, cmd:%s" % headPack)
  print(body.decode())
  print("")

if __name__ == '__main__':
  with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.bind((HOST, PORT))
    s.listen(1)
    conn, addr = s.accept()
    with conn:
      print('Connected by', addr)
      while True:
        data = conn.recv(1024)
        if data:
          # 把數據存入緩沖區(qū)，類似于push數據
          dataBuffer += data
          while True:
            if len(dataBuffer) < headerSize:
              print("數據包（%s Byte）小于消息頭部長度，跳出小循環(huán)" % len(dataBuffer))
              break

            # 讀取包頭
            # struct中:!代表Network order，3I代表3個unsigned int數據
            headPack = struct.unpack('!3I', dataBuffer[:headerSize])
            bodySize = headPack[1]

            # 分包情況處理，跳出函數繼續(xù)接收數據
            if len(dataBuffer) < headerSize+bodySize :
              print("數據包（%s Byte）不完整（總共%s Byte），跳出小循環(huán)" % (len(dataBuffer), headerSize+bodySize))
              break
            # 讀取消息正文的內容
            body = dataBuffer[headerSize:headerSize+bodySize]

            # 數據處理
            dataHandle(headPack, body)

            # 粘包情況的處理
            dataBuffer = dataBuffer[headerSize+bodySize:] # 獲取下一個數據包，類似于把數據pop出

# Python Version:3.5.1
import socket
import time
import struct
import json

host = "localhost"
port = 1234

ADDR = (host, port)

if __name__ == '__main__':
  client = socket.socket()
  client.connect(ADDR)

  # 正常數據包定義
  ver = 1
  body = json.dumps(dict(hello="world"))
  print(body)
  cmd = 101
  header = [ver, body.__len__(), cmd]
  headPack = struct.pack("!3I", *header)
  sendData1 = headPack+body.encode()

  # 分包數據定義
  ver = 2
  body = json.dumps(dict(hello="world2"))
  print(body)
  cmd = 102
  header = [ver, body.__len__(), cmd]
  headPack = struct.pack("!3I", *header)
  sendData2_1 = headPack+body[:2].encode()
  sendData2_2 = body[2:].encode()

  # 粘包數據定義
  ver = 3
  body1 = json.dumps(dict(hello="world3"))
  print(body1)
  cmd = 103
  header = [ver, body1.__len__(), cmd]
  headPack1 = struct.pack("!3I", *header)

  ver = 4
  body2 = json.dumps(dict(hello="world4"))
  print(body2)
  cmd = 104
  header = [ver, body2.__len__(), cmd]
  headPack2 = struct.pack("!3I", *header)

  sendData3 = headPack1+body1.encode()+headPack2+body2.encode()


  # 正常數據包
  client.send(sendData1)
  time.sleep(3)

  # 分包測試
  client.send(sendData2_1)
  time.sleep(0.2)
  client.send(sendData2_2)
  time.sleep(3)

  # 粘包測試
  client.send(sendData3)
  time.sleep(3)
  client.close()

Connected by ('127.0.0.1', 23297)
第1個數據包
ver:1, bodySize:18, cmd:101
{"hello": "world"}

數據包（0 Byte）小于包頭長度，跳出小循環(huán)
數據包（14 Byte）不完整（總共31 Byte），跳出小循環(huán)
第2個數據包
ver:2, bodySize:19, cmd:102
{"hello": "world2"}

數據包（0 Byte）小于包頭長度，跳出小循環(huán)
第3個數據包
ver:3, bodySize:19, cmd:103
{"hello": "world3"}

第4個數據包
ver:4, bodySize:19, cmd:104
{"hello": "world4"}

# Twiested
class MyProtocol(Protocol):
  _data_buffer = bytes()

  # 代碼省略

  def dataReceived(self, data):
    """Called whenever data is received."""
    self._data_buffer += data
    headerSize = 12

    while True:
      if len(self._data_buffer) < headerSize:
        return

      # 讀取消息頭部
      # struct中:!代表Network order，3I代表3個unsigned int數據
      headPack = struct.unpack('!3I', self._data_buffer[:headerSize])
      # 獲取消息正文長度
      bodySize = headPack[1]

      # 分包情況處理
      if len(self._data_buffer) < headerSize+bodySize :
        return

      # 讀取消息正文的內容
      body = self._data_buffer[headerSize:headerSize+bodySize]
      # 處理數據
      self.dataHandle(headPack, body)
      # 粘包情況的處理
      self._data_buffer = self._data_buffer[headerSize+bodySize:]