来回 unix 域套接字锁

Posted 2023-02-23

【中文标题】来回 unix 域套接字锁

【英文标题】：back-and-forth unix domain sockets lock

【发布时间】：2014-07-08 12:46:59

【问题描述】：

我正在编写两个程序，一个用 c++ 编写，另一个用 Python 编写，以使用 unix 域套接字相互通信。我想要做的是让 c++ 代码向 python 代码发送一个数字，然后将另一个数字发送回 c++。这种情况一直持续到 C++ 代码用完要发送的数字并且执行停止。以下是我的代码。我似乎无法在循环的第一次迭代之后运行它们。

我先运行 Python：python code.py /tmp/1 /tmp/2

然后我运行 c++ 代码：./code /tmp/1 /tmp/2

这是输出：

C++ 输出：

发送 0 听力 连接成功 收到 5 已发送 1 听

Python 输出：

听... 收到 (0,) >5 已发送 5 听...

C++ 代码：

static int connFd;

int main(int argc, char* argv[])


   int recv_sock, 
   send_sock;

   struct sockaddr_un server, client;

   ///////////////////////////////////////////
   //                                       
   // setup send             
   //                                       
   ///////////////////////////////////////////

   /* Create socket on which to send. */
   send_sock = socket(AF_UNIX, SOCK_STREAM, 0);
   if (send_sock < 0) 
   
     perror("opening unix socket");
     exit(1);
   

   /* Construct name of socket to send to. */
   client.sun_family = AF_UNIX;

   strcpy(client.sun_path, argv[1]);

   if (connect(send_sock, (struct sockaddr *) &client, sizeof(struct sockaddr_un)) < 0) 
   
     close(send_sock);   
     perror("connecting stream socket");
     exit(1);
   


   ///////////////////////////////////////////
   //                                       
   // setup recv 
   //                                       
   ///////////////////////////////////////////

   recv_sock = socket(AF_UNIX, SOCK_STREAM, 0);

   if(recv_sock< 0)
   
     cerr << "Cannot open socket" << endl;
     return 0;
   

   bzero((char*) &server, sizeof(server));

   server.sun_family = AF_UNIX; 
   strcpy(server.sun_path,  argv[2]);

  //bind socket
  if(bind(recv_sock, (struct sockaddr *)&server, sizeof(server)) < 0)
  
    cerr << "Cannot bind" << endl;
    return 0;
  

  listen(recv_sock, 10);

  int X;
  for (int i = 0; i < 10; i++)
  
    write(send_sock, &i, sizeof(i));
    cout << "sent " << i << endl;
    cout << "Listening" << endl;
    connFd = accept(recv_sock, 0, 0);
    if (connFd < 0)
    
        cerr << "Cannot accept connection" << endl;
        return 0;
    
    else
    
       cout << "Connection successful" << endl;
       read(connFd, &X, sizeof(X));
       cout << "received " << X << endl;
    

    usleep(2000000);

 


 close(send_sock);
 close(recv_sock);
 unlink(argv[2]);
 unlink(argv[1]);


 return 0;

Python 代码：

import socket,os,struct, glob, sys
import random

send_socket = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
recv_socket = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
try:
    os.remove(sys.argv[1])
except OSError:
    pass

recv_socket.bind(sys.argv[1])



recv_socket.listen(10)
while 1:
   print "listening ..."
   conn, addr = recv_socket.accept()
   data = conn.recv(4)


   p = struct.unpack('i',data)
   print 'received ', p

   if p is '9':
      break


   l = int(raw_input(">"))
   a = struct.pack('i', l) 
   send_socket.connect(sys.argv[2])
   send_socket.sendall(a)
   print 'sent ', l

send_socket.close()
conn.close()
recv_socket.close()

我在这种方法中做错了什么？我需要使用线程吗？

谢谢

【参考方案1】：

您在 C++ 代码中处理发送和接收套接字的方式不同：发送套接字在程序开始时绑定一次，而接收套接字在每次迭代时接受一个新连接。

您当前的 Python 实现在 recv_socket 上接受一个新连接，并在每次迭代时连接 send_socket，这解释了您面临的问题。

最有效的解决方法是在循环之前连接每个套接字一次，除非您有充分的理由在每次迭代时打开一个新连接。以下是对应的代码清单：

C++

static int connFd;

int main(int argc, char *argv[]) 

  int recv_sock, send_sock;

  struct sockaddr_un server, client;

  ///////////////////////////////////////////
  //
  // setup send
  //
  ///////////////////////////////////////////

  /* Create socket on which to send. */
  send_sock = socket(AF_UNIX, SOCK_STREAM, 0);
  if (send_sock < 0) 
    perror("opening unix socket");
    exit(1);
  

  /* Construct name of socket to send to. */
  client.sun_family = AF_UNIX;

  strcpy(client.sun_path, argv[1]);

  if (connect(send_sock, (struct sockaddr *)&client,
              sizeof(struct sockaddr_un)) < 0) 
    close(send_sock);
    perror("connecting stream socket");
    exit(1);
  

  ///////////////////////////////////////////
  //
  // setup recv
  //
  ///////////////////////////////////////////

  recv_sock = socket(AF_UNIX, SOCK_STREAM, 0);

  if (recv_sock < 0) 
    cerr << "Cannot open socket" << endl;
    return 0;
  

  bzero((char *)&server, sizeof(server));

  server.sun_family = AF_UNIX;
  strcpy(server.sun_path, argv[2]);

  // bind socket
  if (::bind(recv_sock, (struct sockaddr *)&server, sizeof(server)) < 0) 
    cerr << "Cannot bind" << endl;
    return 0;
  

  listen(recv_sock, 10);
  connFd = accept(recv_sock, 0, 0);
  if (connFd < 0) 
    cerr << "Cannot accept connection" << endl;
    return 0;
   else 
    cout << "Connection successful" << endl;
  

  int X;
  for (int i = 0; i < 10; i++) 
    write(send_sock, &i, sizeof(i));
    cout << "sent " << i << endl;
    cout << "Listening" << endl;
    read(connFd, &X, sizeof(X));
    cout << "received " << X << endl;
    usleep(2000000);
  

  close(send_sock);
  close(recv_sock);
  unlink(argv[2]);
  unlink(argv[1]);

  return 0;

Python

recv_socket = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
send_socket = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
try:
    os.remove(sys.argv[1])
except OSError:
    pass

recv_socket.bind(sys.argv[1])

recv_socket.listen(10)
conn, addr = recv_socket.accept()

send_socket.connect(sys.argv[2])

while 1:
   print "listening ..."
   data = conn.recv(4)
   p = struct.unpack('i',data)
   print 'received ', p

   if p is '9':
      break


   l = int(raw_input(">"))
   a = struct.pack('i', l)
   send_socket.sendall(a)
   print 'sent ', l

send_socket.close()
conn.close()
recv_socket.close()