HELP! BSD select() on socket (WIN/TCP for VMS)

[TAYBENGH%NUSDISCS.BITNET at cunyvm.cuny.edu]

Subject: Re: HELP! BSD select() on socket (WIN/TCP for VMS)

In arctle <9003211059.AA22332 at portia.stanford.edu> Cuong Writes:
>>>gives without setting any fle descriptors (channels). For example,
>>
>>>        if (nfd = (select(sock+1, &ready, &write, &except, &timeout)) <0)
>>>           perror("select");
>>Just take a very sharp look at the code and especially the parentheses.
>> < has a higher priority than =
>>->
>>       if ((nfd = select(sock+1, &ready, &write, &except, &timeout)) <0)
>>          perror("select");
>
>Yes, but it doesn't help explain non-blocking behavior for
>Beng Hang.  What does this perror() report?  Bad access?
>If so, have you considered Holger's comment re. "&read" instead
>of "read"?  What is the actual code?
>
>Good luck,
>
>Cuong

        I admit the mistake made of assigning nfd. Thanks for the correction!
Below is the full source code (written in VAX-C).

In the message <9003202303.AA24028 at uunet.uu.net> sent by Larry Jones:
>Since this is VMS, you might have more luck posting to a VMS news
>group like comp.os.vms rather than a unix group!

        I know I should post it somewhere else, but since there are a lot
of experts in this list, I push my luck. I apologize if I posted wrongly.

-Beng Hang Tay (email address: taybengh at nusdiscs.bitnet)
 Department of Information Systems and Computer Science
 National University of Singapore


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/* Filename     : select_recv.c
   Author       : Beng Hang Tay (taybengh)
   Description  : Test program that receive buffers via stream service
                  using socket accept and recv. Note that raccept routine does
                  not distinguish the source, thus remote_sock is just a
                  memory space that store the incoming struct sockaddr_in value.
*/

#include <sys/types>
#include <sys/socket.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>

main()
{
        int     sock, socklen, size, newsock, flag, nfd;
        struct  sockaddr_in     local_in, remote_in;
        char    inbuf[1024], outbuf[1024], hostname[15], str[10];
        u_short local_port, remote_port;
        fd_set  ready, write, except;
        struct  timeval to;

        printf("pls input the local port (>1000)\n");
        gets(str);
        local_port = atoi(str);
        printf("pls input the source hostname if any\n");
        gets(hostname);
        printf("pls input the source port if any, otherwise 0\n");
        gets(str);
        remote_port = atoi(str);
        printf("pls input the option if any, otherwise default=0\n");
        gets(str);
        flag = atoi(str);

        /* Create socket from which to read */
        sock = socket(AF_INET, SOCK_STREAM, 0);
        if (sock <0)
        {
            perror("opening stream socket");
            exit(1);
        }

        /* create sockaddr */
        local_in.sin_family = AF_INET;
        local_in.sin_addr.s_addr = INADDR_ANY;
        local_in.sin_port = htons(local_port);
        if (bind(sock, &local_in, sizeof(local_in)))
        {
            perror("binding stream socket");
            exit(1);
        }

        /* create sockaddr */
        printf("hostname =%s!\n", hostname);
        remote_in.sin_family = AF_INET;
/*      There is always a acess violation error due to the following
        statement, so it was masked off. The reason unknown!
        remote_in.sin_addr.s_addr = rhost(&hostname);
*/
        remote_in.sin_port = htons(remote_port);

#ifdef BDEBUG
        printf("\n\nbefore accept\n");
        printf("sock: \n");
        printf("family = %d \n", remote_in.sin_family);
        printf("sin_addr.s_addr = %x \n", ntohl(remote_in.sin_addr.s_addr));
        printf("net number = %x \n", inet_netof(remote_in.sin_addr));
        printf("local address part = %x \n", inet_lnaof(remote_in.sin_addr));
        printf("port # = %u\n", ntohs(remote_in.sin_port));
#endif

        listen(sock, 5);
        for (;;)
        {
           /*
            * set the poll time to very large value
            */
           to.tv_sec = 100000;
           to.tv_usec = 100000;
           FD_ZERO(&ready);
           FD_ZERO(&write);
           FD_ZERO(&except);
           FD_SET(sock, &ready);
           FD_SET(sock, &write);
           FD_SET(sock, &except);
           /* Null pointer is not working, giving acess violation problems! */
           if ((nfd = select(sock+1, &ready, &write, &except, 0)) <0)
           {
              perror("select");
              break;
           }

           /*
            * select() always return with nfd set to 1
            */
#ifdef  BDEBUG
        printf("select polling return nfd = %d\n", nfd);
        printf("timeval.tv_sec = %d, tv_usec = %d\n",
                to.tv_sec, to.tv_usec);
        printf("ready = %d, write =%d, except = %d\n",
                ready, write, except);
#endif

           /*
            * NEVER COME INSIDE THE IF
            */
           if (FD_ISSET(sock, &ready))
           {
              socklen = sizeof(remote_in);
              newsock = accept(sock, &remote_in, &socklen);

#ifdef BDEBUG
        printf("\nafter accept\n");
        printf("newsock = %d: \n", newsock);
        printf("family = %d \n", remote_in.sin_family);
        printf("sin_addr.s_addr = %x \n", ntohl(remote_in.sin_addr.s_addr));
        printf("net number = %x \n", inet_netof(remote_in.sin_addr));
        printf("local address part = %x \n", inet_lnaof(remote_in.sin_addr));
        printf("port # = %u\n", ntohs(remote_in.sin_port));
#endif
              if (newsock == -1)
                 perror("accept");
              else
                 for (;;)
                 {
                    /* receive message */
                    if ((size = recv(newsock, inbuf, 1024, flag)) < 0)
                        perror("receiving stream message");
                    if (size == 0)
                       printf("ending connection\n");
                    else
                       printf("received-->%s\n", inbuf);
                    if (inbuf[0] == '\n' || inbuf[0] == '\0')
                       exit(0);

                    /* send message */
                    printf("\nPls input the messages:\n");
                    gets(outbuf);
                    if ((size = send(newsock, outbuf,
                         sizeof(outbuf), flag)) < 0)
                       perror("send");
                    printf("buf sent-->%s, size =%d\n", outbuf, size);
                    if (outbuf[0] == '\n' || outbuf[0] == '\0')
                       exit(0);
                 }
           }
           close(newsock);
        }
}

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