UNIX Network programming: How to use the TCP and UDP callback server programs with the Select function

Server program:

#include <sys/wait.h> #include <string.h> #include <string.h> #include <errno.h> #include <stdio.h> #include <stdlib.h> #include <sys/types.h> #include <sys/socket.h> #include ;signal.h> #include <arpa/inet.h> #include <sys/select.h> #include <sys/time.h> #include <  
unistd.h> #define Serv_port 3334 #define LISTENQ 5 #define Maxline void Str_echo (int sockfd)  
    {ssize_t n;  
      
Char Buf[maxline];  
      
    Again:while ((n = Read (SOCKFD, buf, maxline)) > 0 Write (sockfd, buf, N);  
    if (N < 0 && errno = = eintr) goto again;  
else if (n < 0) perror ("read");  
    } void sig_chld (int signo) {pid_t pid;  
      
    int stat;  
    while (PID = Waitpid ( -1, &stat, Wnohang)) > 0) printf ("Child%d terminated\n", PID);  
Return  
}int main (int argc, char **argv) {int listenfd, CONNFD, UDPFD, Nready, MAXFDP1;  
    Char Mesg[maxline];  
    pid_t Childpid;  
    Fd_set RSet;  
    ssize_t N;  
    Socklen_t Len;  
    const int on = 1;  
    struct sockaddr_in cliaddr, servaddr;  
      
        void sig_chld (int);  
      
    * * 4create listening TCP socket/LISTENFD = socket (af_inet, sock_stream, 0);  
    Bzero (&servaddr, sizeof (SERVADDR));  
    servaddr.sin_family = af_inet;  
    SERVADDR.SIN_ADDR.S_ADDR = htonl (Inaddr_any);  
      
    Servaddr.sin_port = htons (Serv_port);  
    SetSockOpt (LISTENFD, Sol_socket, so_reuseaddr, &on, sizeof (on));  
      
    Bind (LISTENFD, (struct sockaddr *) &servaddr, sizeof (SERVADDR));  
      
        Listen (LISTENFD, Listenq);  
      
    /* 4create UDP socket */UDPFD = socket (af_inet, SOCK_DGRAM, 0); Bzero (&servadDr, sizeof (SERVADDR));  
    servaddr.sin_family = af_inet;  
    SERVADDR.SIN_ADDR.S_ADDR = htonl (Inaddr_any);  
      
    Servaddr.sin_port = htons (Serv_port);  
    Bind (UDPFD, (struct sockaddr *) &servaddr, sizeof (SERVADDR));  Signal (SIGCHLD, SIG_CHLD);  
    /* Must call WAITPID () */Fd_zero (&rset);  
    MAXFDP1 = ((LISTENFD&GT;UDPFD)? listenfd:udpfd) + 1; for (;;)  
        {Fd_set (LISTENFD, &rset);  
        Fd_set (UDPFD, &rset);  
                if (Nready = select (MAXFDP1, &rset, NULL, NULL, NULL) < 0) {if (errno = = eintr)       Continue  
        /* Back to for () */Else Perror ("select");  
            } if (Fd_isset (LISTENFD, &rset)) {len = sizeof (CLIADDR);  
          
            CONNFD = Accept (LISTENFD, (struct sockaddr *) &cliaddr, &len); if ((Childpid = fork ()) = = 0) {/* Child process */CLose (LISTENFD);   /* Close Listening socket * * STR_ECHO (CONNFD);  
            /* Process the request * * exit (0);          Close (CONNFD); /* Parent closes connected socket/} if (Fd_isset (UDPFD, &rset)) {len = size  
            of (CLIADDR);  
      
            n = recvfrom (UDPFD, MESG, Maxline, 0, (struct sockaddr*) &cliaddr, &len);  
        SendTo (UDPFD, MESG, N, 0, (struct sockaddr *) &cliaddr, Len); }  
    }  
}

57-67 Create a well-known port that listens on TCP sockets and bundles the servers, setting the SO_REUSEADDR socket option to prevent existing connections on the port.

70-77 also creates a UDP socket and bundles the same port as the TCP socket. There is no need to set the SO_REUSEADDR socket option before calling bind because the TCP port is independent of the UDP port.

78 Establish a signal handler for SIGCHLD because the TCP connection will be processed by a child process.

83-90 We call select just to wait for the readable condition of the TCP socket or the readable condition of the UDP socket. Since our SIG_CHLD signal processing function may interrupt our call to select, we need to handle the EINTR error.

Author: csdn Blog Ctthuangcheng

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