Error in c socket programming?

Question

int acceptSocket;
struct sockaddr_in addr, client, dest;
char buf[256];
long rc, sentbytes;
int port = 18017;

int CreateSocket()
{



    if(rc!=0)

       {

         printf("socket failure code: %ld\n",rc);

         return 1;

       }

       else

       {

         printf("socket started!\n");

       }

       // Socket creation for UDP

       acceptSocket=socket(AF_INET,SOCK_DGRAM,0);

       if(acceptSocket==-1)

       {

         printf("Failure: socket creation is failed, failure code\n");

         return 1;

       }

       else

       {

         printf("Socket started!\n");

       }

     memset(&addr, 0, sizeof(addr));

     addr.sin_family=AF_INET;

     addr.sin_port=htons(port);

     addr.sin_addr.s_addr=htonl(INADDR_ANY);

     rc=bind(acceptSocket,(struct sockaddr*)&addr,sizeof(addr));

     if(rc==-1)

     {

       printf("Failure: listen, failure code:\n");

       return 1;

     }

     else

     {

       printf("Socket an port %d \n",port);

     }




       while(rc!=-1)
       {
         rc=recvfrom(acceptSocket,buf, 256, 0, (struct sockaddr*) &client, sizeof(client));
         if(rc==0)
         {
           printf("Server has no connection..\n");
           break;
         }
         if(rc==-1)
         {
           printf("failure: recv, failure code\n");
           break;
         }
         XcpIp_RxCallback( (uint16) rc, (uint8*) buf, (uint16) port );


            makeTimer("First Timer", &firstTimerID, 2, 2);   //2ms
            makeTimer("Second Timer", &secondTimerID, 10, 10);    //10ms
            makeTimer("Third Timer", &thirdTimerID, 100, 100);  //100ms

     //    buf[rc]='\0';
     //    printf("Client sendet: %s\n",buf);
     //    sprintf(buf2,"Du mich auch %s",buf);
     //    rc=sendto(connectedSocket,buf2,strlen(buf2),0);

       }


       close(acceptSocket);



       return 0;

     }

I created a socket for udp layer and it is waiting for connection from the client and later sending the data to the client. My program is getting crashed in listen mode. i.e: after bind :I am getting error as

 printf("Failure: listen, failure code:\n");

Could anyone tell me why? @JoachimPileborg: it is not working!! again the same problem. I am not able to comment there.

When you get an error, you can actually see *what* the error is by printing the value of [`errno`](http://pubs.opengroup.org/onlinepubs/9699919799/functions/errno.html). You can get a printable string from the error code by calling [`strerror`](http://pubs.opengroup.org/onlinepubs/009695399/functions/strerror.html). Please edit your question to include the error code (and string). — Some programmer dude, Feb 21 '14 at 10:24
Your code does not show `rc`'s declaration, nor where it is written before the first time it's read. Is that a global variable? And if yes, why? — Medinoc, Feb 21 '14 at 10:26
@user3252048 As UDP isn't connection oriented, you don't actually have clients as such. You have to wait until a client communicates with the server, and then keep track of the clients. — Jayesh Bhoi, Feb 21 '14 at 10:40
@user3252048 please check if port already in use or not give the out put of `netstat -a | grep "18017"` — Jayesh Bhoi, Feb 21 '14 at 10:50
http://www.cs.ucsb.edu/~almeroth/classes/W01.176B/hw2/examples/udp-server.c — user3252048, Feb 21 '14 at 10:52
@user3252048 Can you be more specific? Was it an illegal port number? Was it in use? What *was* the problem, and how did you solve it? — Some programmer dude, Feb 21 '14 at 11:02
If i recieve a request from the client then the recieve is failure. Why so ?? — user3252048, Feb 21 '14 at 11:45

Jayesh Bhoi · Accepted Answer · 2014-02-21T12:43:52.177

-1

First of all you need to find actual error.you can do as follows

As bind man page

On error, -1 is returned, and errno is set appropriately.

The standard procedure in every POSIX call, there is an integer named errno that contains the value of the actual error. You can either check its value manually, or use primitives as perror or strerror

if (rc  == -1) 
{
    perror("socket error");
}

must have #include<errno.h>

Now bind fails many reason one of it like

Probably some other application is listening on that port. You can find this by running

netstat -a | grep "18017"

So if you found port in use then switch to another port number or simply kill that process which uses that port.

Also please update you while...loop in proper format like no need to compare rc to both -1 and 0 please do as follows

   while(1)
   {
        //try to receive some data, this is a blocking call
        if ((rc = recvfrom(acceptSocket, buf, 256, 0, (struct sockaddr *) &client, &client)) == -1)   // read datagram from server socket
        {
            break;
        }
       //rest of your code
    }

edited Feb 21 '14 at 12:43

answered Feb 21 '14 at 10:58

Jayesh Bhoi

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i had a problem with port number. – user3252048 Feb 21 '14 at 11:00
If i recieve a request from the client then the recieve is failure. Why so ?? – user3252048 Feb 21 '14 at 11:44
@user3252048 please look updated post. – Jayesh Bhoi Feb 21 '14 at 11:59
i modified as you said but then alsi it is not recieving any data from client. why so ?? – user3252048 Feb 21 '14 at 12:30
@user3252048 is client send any data? – Jayesh Bhoi Feb 21 '14 at 12:31
In my code : rc = recvfrom(); so i was calling this api with XcpIp_RxCallback( (uint16) rc, (uint8*) buf, (uint16) port ); //if I do as your then what should I use for the first parameter ?? – user3252048 Feb 21 '14 at 12:41
@user3252048 please see my edited answer for `while..loop` – Jayesh Bhoi Feb 21 '14 at 12:44

Error in c socket programming?

1 Answers1