如何在C++ Web服务器中为多个客户端修复使用select()和send()时的Error 141。

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英文:

How to fix Error 141 when using select() and send() in C++ web server for multiple clients

问题

我正在构建一个用C++编写的Web服务器，需要同时为多个客户端提供服务，而不会阻塞任何单个客户端。为了实现这一目标，我正在使用select()函数。

当一个客户端在我发送响应时（在这种情况下，是一个长视频）关闭连接时，我遇到了一个错误。程序以状态141退出，在使用LLDB进行调试时，似乎正是在send()函数中发生的，当尝试发送到一个不再存在的套接字时，因为客户端关闭了连接。

在这种情况下，我是否遗漏了什么，或者需要以不同的方式处理？

在我的代码中，我有以下设置：

  1. // 代码部分不翻译

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英文:

I'm working on building a web server in C++ that needs to serve multiple clients simultaneously without blocking any individual client. To achieve this, I'm using the select() function.

I'm encountering an error when a client closes the connection while I'm sending a response (in this case, a long video). The program exits with status 141, and upon debugging with LLDB, it seems to happen exactly in the send() function when trying to send to a socket that no longer exists because the client closed the connection.

Is there something I'm missing, or need to handle differently, in this situation?

I have the following setup in my code:

  1. void    Error(const char *msg)
  2. {
  3.     perror(msg);
  4.     exit(1);
  5. }
  7. void    Server::Init()
  8. {
  9.     memset(&server_infos, 0, sizeof(server_infos));
  10.     server_infos.ai_family      = AF_INET;
  11.     server_infos.ai_protocol    = SOCK_STREAM;
  12.     getaddrinfo(LOCALHOST, PORT, &server_infos, &sinfo_ptr);
  13. }
  15. void    Server::CreateServer()
  16. {
  17.     Init();
  18.     if ((server_socket = socket(sinfo_ptr->ai_family, sinfo_ptr->ai_protocol, 0)) == -1)
  19.        Error("Error: Creating socket failed\n");
  20.     int optval = 1;
  21.     setsockopt(server_socket, SOL_SOCKET, SO_REUSEPORT, &optval, sizeof(optval));
  22.     if (bind(server_socket, sinfo_ptr->ai_addr, sinfo_ptr->ai_addrlen) == -1)
  23.        Error("Error: Binding failed\n");
  24.     if (listen(server_socket, FD_SETSIZE) == -1)
  25.        Error("Error: Listening failed\n");
  26. }
  28. void Server::SendResponseHeader(int clt_skt)
  29. {
  30.     char response_header[] =    "HTTP/1.1 200 OK\r\n"
  31.                                 "Server: Allah Y7ssen L3wan\r\n"
  32.                                 "Content-Length: 82013359\r\n"
  33.                                 "Content-Type: video/mp4\r\n\r\n";
  34.     if (send(clt_skt, response_header, strlen(response_header), 0) == -1)
  35.         Error("Error (Send) -> ");
  36. }
  38. void Server::DropClient()
  39. {
  40.     close(active_clt);
  41.     FD_CLR(active_clt, &readfds);
  42.     FD_CLR(active_clt, &writefds);
  43.     _clients.erase(itb);
  44.     close(itb->GetCltFd());
  45.     std::cerr << "Connection Closed\n";
  46. }
  49. int Server::AcceptAddClientToSet()
  50. {
  51.     int newconnection = accept(server_socket, (struct sockaddr *)&storage_sock, &clt_addr);
  52.     if (newconnection == -1)
  53.         Error("Error (Accept) -> ");
  54.     const char *path = "/Users/me/Desktop/video.mp4";
  55.     _clients.push_back(Client(newconnection, open(path, O_RDONLY)));
  56.     client_write_ready = false;
  57.     FD_SET(_clients.back().GetCltSocket(), &readfds);
  58.     FD_SET(_clients.back().GetCltSocket(), &writefds);
  59.     if (_clients.back().GetCltSocket() > maxfds)
  60.         maxfds = _clients.back().GetCltSocket();
  61.     return (newconnection);
  62. }
  64. void Server::Start()
  65. {
  66.     CreateServer();
  67.     
  68.     FD_ZERO(&readfds);
  69.     FD_ZERO(&writefds);
  70.     FD_SET(server_socket, &readfds);
  71.     FD_SET(server_socket, &writefds);
  72.     maxfds = server_socket;
  73.     bytesreceived = 0;
  75.     while (TRUE)
  76.     {
  77.         tmpfdsread = readfds;
  78.         tmpfdswrite = writefds;
  79.         activity = select(maxfds + 1, &tmpfdsread, &tmpfdswrite, NULL, NULL);
  80.         if (activity == -1)
  81.            Error("Error (Select) -> ");
  82.         if (FD_ISSET(server_socket, &tmpfdsread))
  83.             client_socket = AcceptAddClientToSet();
  84.         for (itb = _clients.begin(); itb != _clients.end(); itb++)
  85.         {
  86.             active_clt = itb->GetCltSocket();
  87.             if (FD_ISSET(active_clt, &tmpfdsread) && !client_write_ready)
  88.             {
  89.                 bytesreceived = recv(active_clt, requested_data, sizeof(requested_data), 0);
  90.                 if (bytesreceived <= 0)
  91.                 {
  92.                     DropClient();
  93.                     std::cerr << "Connection Closed\n";
  94.                 }
  95.                 else
  96.                 {
  97.                     client_write_ready = true;
  98.                     SendResponseHeader(active_clt);
  99.                 }
  100.             }
  102.             if (FD_ISSET(active_clt, &tmpfdswrite) && client_write_ready)
  103.             {
  104.                 bytesread = read(itb->GetCltFd(), buffer, sizeof(buffer));
  105.                 if (bytesread == -1)
  106.                     Error("Error (Read) -> ");
  107.                 bytessent = send(active_clt, buffer, bytesread, 0);
  108.                 if (bytessent == -1)
  109.                 {
  110.                     std::cout << "Cannot Send\n";
  111.                         Error("Error (Send) -> ");
  112.                 }
  113.                 if (bytesread == 0)
  114.                 {
  115.                     DropClient();
  116.                     std::cout << "Done With This Client ->" <<  itb->GetCltFd() << "\n";
  117.                 }
  118.             }
  119.         }
  120.     }
  121.     close(server_socket);
  122. }

答案1

得分: 0

Ignoring the SIGPIPE signal using signal(SIGPIPE, SIG_IGN) 允许程序继续运行，即使写入/发送操作由于关闭/无效的套接字而失败。

https://stackoverflow.com/questions/108183/ 有帮助。

英文:

Ignoring the SIGPIPE signal using signal(SIGPIPE, SIG_IGN) allows the program to continue running even if the write/send operation fails due to a closed/invalid socket.

https://stackoverflow.com/questions/108183/ is helpful.

huangapple
  • 本文由 发表于 2023年6月6日 15:19:36
  • 转载请务必保留本文链接：https://go.coder-hub.com/76412255.html
  • c++
  • nonblocking
  • sockets
  • webserver
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