通过python套接字接收ctypes`c_wchar_p`的问题python 3.7.7

编程问答 2022-05-31

问题描述

（Windows 10、x64、PyCharm）

短篇小说：我在 python 服务器脚本中遇到了 payload_in.event 和 payload_out.event 问题。两者都来自 c_wchar_p 类型，后者来自 ctypes。

长话： 我目前正在使用 python 处理客户端和服务器。它们通过 127.0.01:6666 上的 TCP/IP 套接字进行通信。我正在使用模块 Ctypes 发送和接收类似 c 的结构。一切正常，我可以发送/接收数组、整数、浮点数并在双方使用它们，但我发现在 python 服务器脚本中打印 payload_in.event 和 payload_out.event 时存在错误，两者都c_wchar_p 类型。

在客户端脚本中，我可以完美地访问和打印 payload_in.event 和 payload_out.event ***但是即使代码相同，我的服务器脚本也不能。 . .

在服务器脚本中，打印 payload_in.event 和 payload_out.event 会导致两个程序暂停 10 秒左右，然后客户端控制台告诉我与服务器的连接已关闭。

如果我在 python 服务器脚本中注释掉 payload_in.event 和 payload_out.event 的打印，一切正常。我不知道如何解决这种行为，如果有人能帮助我，我会很高兴。

beagleServer.py

import socket
from ctypes import *


class Struct(Structure):
    _fields_ = [("id",c_uint32),# 4B
                ("prio",# 4B
                ("event",c_wchar_p),# 8B
                ("data",c_float * 10)]  # 40B


def main():
    BUFFSIZE = sizeof(Struct)
    host = '127.0.0.1'
    port = 6666

    beagleServer = socket.socket()
    beagleServer.bind((host,port))
    beagleServer.listen(1)

    print("Server is listening on " + host + ":" + str(port) + "!")
    client,clientAddress = beagleServer.accept()
    print("Connection from: " + str(clientAddress[0]) + ":" + str(clientAddress[1]))

    # receiving payload
    buffer = client.recv(BUFFSIZE)
    payload_in = Struct.from_buffer_copy(buffer)
    print("\nPayload of ",sizeof(payload_in)," Bytes has been received successfully: ",payload_in,"\nPayload.id: ",payload_in.id,"\nPayload.prio: ",payload_in.prio,"\nPayload.event: ",payload_in.event,"\nPayload.data: ",list(payload_in.data),"\nReceived buffer: ",buffer)

    # sending back payload
    payload_out = payload_in
    transferredBytes = client.send(payload_out)
    print("\nPayload of ",transferredBytes," Bytes has been sent successfully: ",payload_out,payload_out.id,payload_out.prio,payload_out.event,list(payload_out.data))

    print("Closing server socket!")
    client.close()

if __name__ == '__main__':
    main()

beagleClient.py

import socket
from ctypes import *


class Struct(Structure):
    _fields_ = [("id",c_float * 10)]  # 40B


beagleServer = ('127.0.0.1',6666)
beagleClient = socket.socket(socket.AF_INET,socket.soCK_STREAM)
beagleClient.connect(beagleServer)
print("Connection with server has been established!")

# Creating the Struct
payload_out = Struct(390897,"activateMode1",(3.12,4.21,1.23))
print("\nPayload of ",sizeof(payload_out)," Bytes has been created successfully: ",list(payload_out.data))

# Sending
bytesTransferred = beagleClient.send(payload_out)
print("\nPayload of ",bytesTransferred," Bytes has been sent!")

# Receiving
BUFFSIZE = sizeof(Struct)
buffer = beagleClient.recv(BUFFSIZE)
payload_in = Struct.from_buffer_copy(buffer)
print("\nPayload of ",list(payload_in.data))

print("Closing the connection to ",beagleServer,"!")
beagleClient.close()

解决方法

Struct.event 是一个指针。在两个进程之间传输的指针只是一个地址，在另一个进程中没有任何意义。改用数组：

("event",c_wchar * 80)

它仍然可以用同样的方式初始化，但不能超过传输字符串的数组大小。此外 c_wchar 大小因架构而异，因此您可能希望使用 c_char * 80 代替，然后对字符串进行编码/解码，例如payload.event = 'some string'.encode()（或仅使用字节字符串：b'some string'）。

ctypespythonpython-sockets