Help! UDP Recv Not Working...

I think you should use recvfrom instead recv  as you are using UDP. i have written program in windows for UDP socket communication

i can send the code if u want( the code wrtten using winsock API)

 it works only for windows not for symbian:

simple echo program:

// Client Program

#include <WinSock.h>
#include <stdio.h>
#include <iostream.h>

#define SERVER_PORT 4000

void Initialize() {
   WORD wVersionRequested;
   WSADATA wsaData;
   int err;

   wVersionRequested = MAKEWORD( 1, 1 );

   err = WSAStartup( wVersionRequested, &wsaData );
   if ( err != 0 ) {
      /* Tell the user that we couldn't find a useable */
      /* winsock.dll.                                  */
      printf("\n couldn't find a useable winsock.dll");
      exit(1);
   }

   /* Confirm that the Windows Sockets DLL supports 1.1.*/
   /* Note that if the DLL supports versions greater    */
   /* than 1.1 in addition to 1.1, it will still return */
   /* 1.1 in wVersion since that is the version we      */
   /* requested.                                        */

   if ( LOBYTE( wsaData.wVersion ) != 1 ||
          HIBYTE( wsaData.wVersion ) != 1 ) {
      /* Tell the user that we couldn't find a useable */
      /* winsock.dll.                                  */
      WSACleanup( );
      printf("\n couldn't find a useable winsock.dll");
      exit(1);
   }
}

int main()
{
   SOCKET            sockfd;
   SOCKADDR_IN         servaddr,cliaddr;
   int sin_size = sizeof(struct sockaddr_in);
    char recvline[100];
   char sendStr[100];
   int n;

   Initialize();

   servaddr.sin_family = AF_INET;
   servaddr.sin_addr.s_addr = inet_addr("10.6.21.13");
   servaddr.sin_port = htons(SERVER_PORT);
      

      sockfd = socket(AF_INET, SOCK_DGRAM, 0);

        cout<<"UDP socket created with ID ="<<sockfd<<endl;
      
      while(1) // always true
      {
            cout<<endl<<"Enter string or write exit to quit"<<endl;
            cin>>sendStr;
      
            if(strcmp("exit",sendStr)==0)
               exit(0);
            sendto(sockfd, sendStr, strlen(sendStr), 0, (LPSOCKADDR) &servaddr, sin_size);
            n = recvfrom(sockfd, recvline, 100, 0, (LPSOCKADDR) &cliaddr,  &sin_size);
            recvline[n] = '\0';   /* null terminate */   
            cout<<"Received from Server    = "<<recvline<<endl;
            
      }

   return 0;
}

===================================

//Server Program:


#include <WinSock.h>
#include <stdio.h>
#include <iostream.h>
#define SERVER_PORT 4000


void Initialize() {
   WORD wVersionRequested;
   WSADATA wsaData;
   int err;

   wVersionRequested = MAKEWORD( 1, 1 );

   err = WSAStartup( wVersionRequested, &wsaData );
   if ( err != 0 ) {
      /* Tell the user that we couldn't find a useable */
      /* winsock.dll.                                  */
      printf("\n couldn't find a useable winsock.dll");
      exit(1);
   }

   /* Confirm that the Windows Sockets DLL supports 1.1.*/
   /* Note that if the DLL supports versions greater    */
   /* than 1.1 in addition to 1.1, it will still return */
   /* 1.1 in wVersion since that is the version we      */
   /* requested.                                        */

   if ( LOBYTE( wsaData.wVersion ) != 1 ||
          HIBYTE( wsaData.wVersion ) != 1 ) {
      /* Tell the user that we couldn't find a useable */
      /* winsock.dll.                                  */
      WSACleanup( );
      printf("\n couldn't find a useable winsock.dll");
      exit(1);
   }
}


int   main()
{
   SOCKET            sockfd;
   int               n;
   SOCKADDR_IN         servaddr, cliaddr;
    char            mesg[100];
    int sin_size = sizeof(struct sockaddr_in);

   Initialize();

   sockfd = socket(AF_INET, SOCK_DGRAM, 0);

   cout<< "Socket Created with ID" <<sockfd<<endl;

   servaddr.sin_family      = AF_INET;
   servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
   servaddr.sin_port        = htons(SERVER_PORT);
   memset(&(servaddr.sin_zero), 0, 8 );

   if(bind(sockfd, (LPSOCKADDR) &servaddr, sizeof(servaddr))==0)
      cout<<"Bind operation successfully done"<<endl;
   else
      cout<<"Bind operation failed"<<endl;

   while(1)
   {
      
      n = recvfrom(sockfd, mesg, 100, 0,(LPSOCKADDR) &cliaddr,  &sin_size);
      mesg[n] = '\0';   /* null terminate */   
      cout<<"Message Received           :"<<mesg<<endl<<endl<<endl;
      sendto(sockfd, mesg, strlen(mesg), 0, (LPSOCKADDR) &cliaddr,  sin_size);
      printf("Message Sent back to client : %s\n",mesg);
   }

   return 0;
}

When you use winsock, and sockets don't work, the problem has nothing to do with Symbian OS (it is bypassed). The problem is ALWAYS either in winsock or some error in the application.


You may have different problem there. The first thing there is to get the connection up and working: does your server receive the packet and reply to it in GPRS case?


Then that that means: on emulator winsock does not get the packet, or on the phone symbian stack does not get the packet. Or the return packet is somehow faulty:


Just to be sure, you have then verified that the ports and addresses of your return packet exactly match the addresses in you outgoing packet (src/dst reversed)?