使用python和ctype通过套接字发送/接收数据结构

Question

我试图从一个python客户端向服务器发送和接收C结构数据，反之亦然。客户端和服务器都可以在连接和交换数据方面顺利进行。客户端向服务器发送ctype结构，服务器再次发送它。问题是我不知道如何解释客户端收到的消息，并以结构格式提取数据。我最后的想法是让一个python服务器和C客户端相互交谈并以预定义的结构交换数据。

这里是代码我有一个客户端和服务器在Python：

客户端代码

import socket 
import sys 
import time 

from ctypes import * 

class payload_t(Structure): 
    _fields_ = [("ms", c_ulong), 
       ("counter", c_ulong), 
       ("DHT_temperature", c_float), 
       ("DHT_humidity", c_float), 
       ("DS_temperature", c_float), 
       ("temperature_setpoint", c_float), 
       ("time_setpoint", c_float)] 

# Create a TCP/IP socket 
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) 

# Connect the socket to the port where the server is listening 
server_address = ('localhost', 10000) 
print >>sys.stderr, 'connecting to %s port %s' % server_address 
sock.connect(server_address) 

try: 
    for i in range(0,10): 
     # Send data 
     payload=payload_t(i*1000,i+1,25.2,45.7,25.8,33.22,3600.0) 
     message = payload 
     # 'This is the message. It will be repeated.' 
     print 'length of message %d' % sizeof(message) 
     print 'sending "', message.ms, message.counter, message.DHT_temperature, message.DHT_humidity, message.DS_temperature, message.temperature_setpoint, message.time_setpoint, '"' 
     sock.sendall(message) 
     # time.sleep(0.1) 
     # Look for the response 
     amount_received = 0 
     amount_expected = sizeof(message) 

     while amount_received < amount_expected: 
      datap = sock.recv(sizeof(message)) 
      amount_received += len(datap) 
     print >>sys.stderr, 'received "%s"' % datap 
     print type(datap) 
     payload=payload_t() 
     datap.readinto(payload) 
     data=datap.readinto(payload_t) 
     data=struct.unpack(payload_t,datap) 
      print 'Received "', data.ms, data.counter, data.DHT_temperature, data.DHT_humidity, data.DS_temperature, data.temperature_setpoint, data.time_setpoint, '"' 

finally: 
    print >>sys.stderr, 'closing socket' 
    sock.close() 

服务器代码

import socket 
import sys 
from ctypes import * 

class payload_t(Structure): 
    _fields_ = [("ms", c_ulong), 
       ("counter", c_ulong), 
       ("DHT_temperature", c_float), 
       ("DHT_humidity", c_float), 
       ("DS_temperature", c_float), 
       ("temperature_setpoint", c_float), 
       ("time_setpoint", c_float)] 

# Create a TCP/IP socket 
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) 

# Bind the socket to the port 
server_address = ('localhost', 10000) 
print >>sys.stderr, 'starting up on %s port %s' % server_address 
sock.bind(server_address) 

# Listen for incoming connections 
sock.listen(1) 
payload=payload_t(0,0,0.0,0.0,0.0,0.0,0.0) 
while True: 
    # Wait for a connection 
    print >>sys.stderr, 'waiting for a connection' 
    connection, client_address = sock.accept() 

    try: 
     print >>sys.stderr, 'connection from', client_address 

     # Receive the data in small chunks and retransmit it 
     while True: 
      data = connection.recv(sizeof(payload)) 
      print >>sys.stderr, 'received "%s"' % data 
      if data: 
       print >>sys.stderr, 'sending data back to the client' 
       connection.sendall(data) 
      else: 
       print >>sys.stderr, 'no more data from', client_address 
       break 

    finally: 
     # Clean up the connection 
     connection.close() 

Answer 1

首先，您目前倾倒收到的数据。您在每次循环迭代中重新分配变量'datap'。

做这样的事情，而不是：

datap += sock.recv(sizeof(message) - amount_received) 

（当然，这还不是最高效的代码，但你的想法。）

当你有你的结构在“从datap”变种组装，使用'from_buffer'或'from_buffer_copy'方法将其加载到ctype类中。

payload = payload_t.from_buffer_copy(datap) 

后者在您的情况下更好，因为当您重新绑定'datap'var时，缓冲区可能会消失。