世論調査（）ソケットプログラミングTCPのLinuxの複数の接続の問題

Question

私はプログラミングソケットに新しいんだけど、私はhttps://www.ibm.com/support/knowledgecenter/ssw_ibm_i_71/rzab6/poll.htmでのIBMの例を踏襲し、それを改善するためにいくつかのコードを変更しましたが、私はのtelnet IPポートを介してサーバに接続するとき、および接続する最初のクライアントではメッセージをエコーし​​ますが、2番目にはメッセージをエコーし​​ません。私は（真の）中でループので、それはバックアップの代わりに行くのデータをrecvをし、リストに新しい接続を追加しようとしているループ保持ので、それがあったああ

#include <netinet/in.h> // sockaddr_in struct 
#include <arpa/inet.h> //inet_addr() 
#include <sys/socket.h> 
#include <errno.h> //errors 
#include <stdio.h> //perror() 
#include <cstdlib> //EXIT_FAILURE 
#include <sys/ioctl.h> //FIONBIO 
#include <unistd.h> //close file descriptor 
#include <fcntl.h> //make non blocking 
#include <poll.h> //poll stuff 
#include <string.h> //memset 
int main() 
{ 
    int s = -1; 
    int rc; 
    int optval = 1; 
    int timeout; 
    bool end_server = false; //because we need to log if EWOULDBLOCK is true... 

    struct pollfd fds[200]; //initialize pollfd struct 
    int nfds = 1; // nfds_t really set to 1 else it will be 199 once we pass it to poll.... 

    int current_size = 0; 

    int new_s = -1; 

    int close_conn; 

    char *buff; 

    int len; 

    bool compress_array; 

    s = socket(AF_INET, SOCK_STREAM, 0); 

    //make socket description reusable with SO_REUSEADDR 
    rc = setsockopt(s, SOL_SOCKET, SO_REUSEADDR, reinterpret_cast<char*>(&optval), sizeof(optval)); 
    if(rc < 0){ 
     perror("setsockopt()"); 
     close(s); 
     exit(EXIT_FAILURE); 
    } 

    //make socket non-blocking 
    //rc = ioctl(s, FIONBIO, reinterpret_cast<char*>(&optval)); 
    //if(rc < 0) 
    //{ 
    // perror("ioctl()"); 
    // close(s); 
    // exit(EXIT_FAILURE); 
    //} 
    fcntl(s, F_SETFL, O_NONBLOCK); 

    struct sockaddr_in saddr; 
    //initialize sockaddr_in struct 
    memset(&saddr, 0, sizeof(saddr)); 

    saddr.sin_family = AF_INET; 
    saddr.sin_port = htons(80); 
    saddr.sin_addr.s_addr = inet_addr("127.0.0.1"); 

    rc = bind(s, reinterpret_cast<struct sockaddr *>(&saddr), sizeof(saddr)); 

    if(rc < 0){ 
     perror("bind()"); 
     exit(EXIT_FAILURE); 
    } 

    rc = listen(s, 32); 
    if(rc < 0){ 
     perror("listen() failed"); 
     close(s); 
     exit(EXIT_FAILURE); 
    } 

    //initialize fds struct 
    memset(&fds, 0, sizeof(fds)); 

    fds[0].fd = s; 
    fds[0].events = POLLIN; //check if data to read 

    //initialize timeout value to 3 mins based on millisecs 
    //timeout = (3 * 60 * 1000); // because function will be like sleep() that uses millisecs 
    timeout = 10000; 

    do{ 
     //call poll() and wait 3 mins to complete because of timeout 
     printf("Waiting on poll()...\n"); 
     rc = poll(fds, nfds, timeout); 

     if(rc < 0){ 
      perror("poll() failed"); 
      exit(EXIT_FAILURE); 
     } 

     //check if 3 minutes timeout expired 
     if(rc == 0){ 
      printf("poll() timed out ending program...\n"); 
      exit(EXIT_FAILURE); 
     } 

     current_size = nfds; 
     for(int i = 0; i < current_size; i++) 
     { 
      //loop thru fds and check if revents returns POLLIN, means the fd have data to read... 
      if(fds[i].revents == 0) 
       continue; 


      //if revents is not POLLIN then exit program and log 
      if(fds[i].revents != POLLIN){ 
       printf("revents != POLLIN, revents = %d\n", fds[i].revents); 
       //end_server = true; 
       //break; 
       //perror("revents unknown"); 
       //exit(EXIT_FAILURE); 
       close(fds[i].fd); 
       fds[i].fd = -1; 
       break; 
      } 

      if(fds[i].fd == s){ 
       printf("Listening socket available\n"); 

       do{ 
        //accept each new incoming connections 
        new_s = accept(s, NULL, NULL); 
        if(new_s < 0){ 
         if(errno != EWOULDBLOCK){ 
          perror("accept() failed because of socket would block"); 
          end_server = true; 
         } 
         //printf("something else wrong with accept()\n"); 
         break; 
        } 

        //add new incoming connection 
        printf("new incoming connection - nfds: %d\n", new_s); 
        fds[nfds].fd = new_s; 
        fds[nfds].events = POLLIN; 
        nfds++; 
        //continue; 
        //loop back up and accept another connection 

       } while(new_s != -1); 
      } 
      // file descriptor is readable because its now new_s instead of s 
      else { 
       printf("descriptor %d is readable\n", fds[i].fd); 
       close_conn = false; 
       //receive all data on this connection till we go back and poll again 
       do { 

        rc = recv(fds[i].fd, reinterpret_cast<void*>(&buff), sizeof(buff), 0); 
        if(rc < 0){ 
         if(errno != EWOULDBLOCK){ 
          perror("recv() failed"); 
          close_conn = true; 
         } 
         break; 
        } 

        //check if conn was closed by client 
        if(rc == 0){ 
         printf("connection closed"); 
         close_conn = true; 
         break; 
        } 

        //data was received 
        len = rc; 
        printf("%d bytes received", len); 

        //process stuff or echo data back to client 
        rc = send(fds[i].fd, reinterpret_cast<void*>(&buff), sizeof(buff), 0); 
        if(rc < 0){ 
         perror("send() failed"); 
         close_conn = true; 
         break; 
        } 
        memset(&buff, 0, sizeof(buff)); 

       } while (true); 
       if(close_conn){ 
        close(fds[i].fd); 
        fds[i].fd = -1; 
        compress_array = true; 
       } 

      } 


     } 
     if(compress_array){ 
      compress_array = false; 
      int i = 0; 
      for(i = 0; i < nfds; i++){ 
       if(fds[i].fd == -1){ 
        for(int j = i; j < nfds; j++){ 
         fds[j].fd = fds[j+1].fd; 
        } 
        i--; 
        nfds--; 
       } 
      } 
     } 

    } while (end_server == false); 

    //clean all sockets that are open 
    for(int i = 0; i < nfds; i++){ 
     if(fds[i].fd > 0){ // if already -1 don't need to close socket 
      close(fds[i].fd); 
      fds[i].fd = -1; 
     } 
    } 



    return 0; 
} 

Answer 1

。