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TCP/IP program of TELNET protocol to the given host and port

Posted By: Milind Mishra     Category: Networking     Views: 3662

TCP/IP program of TELNET protocol to the given host and port.

Code for TCP/IP program of TELNET protocol to the given host and port in Networking

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/signal.h>
#include <sys/errno.h>

#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

#include "local.h"void    rcvurg(int);

#define    BUFSIZE        2048    /* read buffer size    */struct termios    oldtty;

int    connectTCP(constchar *host, constchar *service);
int    ttysetup(void);

/*------------------------------------------------------------------------ * telnet - do the TELNET protocol to the given host and port *------------------------------------------------------------------------ */int
telnet(constchar *host, constchar *service)
{
    int    s, nfds;    /* socket and # file descriptors */
    u_char    buf[BUFSIZE];
    int    cc;
    int    on = 1;
    fd_set    arfds, awfds, rfds, wfds;
    FILE    *sfp;

    s = connectTCP(host, service);

    ttysetup();

    fsmbuild();    /* set up FSM's */

    (void) signal(SIGURG, rcvurg);
    (void) setsockopt(s, SOL_SOCKET, SO_OOBINLINE, (char *)&on,
            sizeof(on));

    nfds = getdtablesize();
    FD_ZERO(&arfds);
    FD_ZERO(&awfds);
    FD_SET(s, &arfds);    /* the socket            */
    FD_SET(0, &arfds);    /* standard input        */

    sfp = fdopen(s, "w");    /* to get buffered output    */while (1) {
        memcpy(&rfds, &arfds, sizeof(rfds));
        memcpy(&wfds, &awfds, sizeof(rfds));

        if (select(nfds, &rfds, &wfds, (fd_set *)0,
                (struct timeval *)0) < 0) {
            if (errno == EINTR)
                continue;    /* just a signal    */
            cerrexit("select: %s\n", strerror(errno));
        }
        if (FD_ISSET(s, &rfds)) {
            cc = read(s, (char *)buf, sizeof(buf));
            if (cc < 0)
                cerrexit("socket read: %s\n",
                        strerror(errno));
            elseif (cc == 0) {
                printf("\nconnection closed.\n");
                if (tcsetattr(0, TCSADRAIN, &oldtty) < 0)
                    errexit("tcsetattr: %s\n",
                        strerror(errno));
                exit(0);
            } else
                ttwrite(sfp, stdout, buf, cc);
        }
        if (FD_ISSET(0, &rfds)) {
            cc = read(0, (char *)buf, sizeof(buf));
            if (cc < 0)
                cerrexit("tty read: %s\n",
                        strerror(errno));
            elseif (cc == 0) {
                FD_CLR(0, &arfds);
                (void) shutdown(s, 1);
            } else
                sowrite(sfp, stdout, buf, cc);
        }
        (void) fflush(sfp);
        (void) fflush(stdout);
    }
}
  
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Milind Mishra
Milind Mishra author of TCP/IP program of TELNET protocol to the given host and port is from India.
 
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