Winsock Help

This is a discussion on Winsock Help within the C Programming forums, part of the General Programming Boards category; I am trying to code a basic command line server, basically so I can telnet to it and send data ...

  1. #1
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    Winsock Help

    I am trying to code a basic command line server, basically so I can telnet to it and send data and the server will print it out.

    Code:
    #include <stdio.h>
    #include <windows.h>
    #include <winsock2.h>
    
    
    int main()
    
    {
    int servSock;
    int clntSock;
    struct sockaddr_in echoServAddr;
    struct sockaddr_in echoClntAddr;
    unsigned short echoServPort;
    unsigned int clntLen;
    WSADATA wsaData;
    char echoBuffer[100];
    int recvMsgSize;
    
    
    WSAStartup(MAKEWORD(2, 0), &wsaData);
    servSock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
    
    
    
    echoServAddr.sin_family = AF_INET;
    echoServAddr.sin_addr.s_addr = htons(INADDR_ANY);
    echoServAddr.sin_port = htons(21);
    
    
    bind(servSock, (struct sockaddr *) &echoServAddr, sizeof(echoServAddr));
    listen(servSock, 5);
    clntSock = accept(servSock, (struct sockaddr *) &echoClntAddr, &clntLen);
    
    while (1)
    {
    sleep(2000);
    
    recv(servSock, echoBuffer, 0, 0);
    printf("%s", echoBuffer);
    
    }
    
    printf("%s", echoBuffer);
    return 0;
    
    }

    I want to print out all the data received, when I use a loop though it like prints out things in the buffer that haven't been sent "ZZZZZZZ"

    So basically can anybody help me.
    Sorry for not giving much information.

  2. #2
    Climber spoon_'s Avatar
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    look at the MSDN page for recv. you're not specifying the size of the buffer.
    {RTFM, KISS}

  3. #3
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    in addition to what spoon_ said in his post, you need to recv() on "clntSock" cause thats the connected socket returned by accpet().

    also, data received by recv() is not terminated with null. So using printf() on the the received string without null terminator can be dangerous as it may cause segmentation fault. So make sure you null terminate the echoBuffer with null after receive returns like this.

    Code:
    int rc;
    
    clntSock = accept(servSock, (struct sockaddr *) &echoClntAddr, &clntLen);
    
    while (1)
    {
        
        rc = recv(clntSock, echoBuffer, sizeof(echoBuffer) - 1, 0); /* Always check return value of recv() */
      
        if (rc == 0) { printf("Connection closed\n"); exit(0);}
        if (rc == -1) {printf("Error in recv\n"); exit(0);}
        
        echoBuffer[rc] = '\0';    /* null terminated the received buffer */
        printf("%s", echoBuffer);
    
    }

  4. #4
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    Thank you for your help.

    nkhambal when I use that code it tells me, that there is an error with the winsock.

  5. #5
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    What errors?

    Check the return value of accept() ("clntSock") before using it in recv().

    Code:
    clntSock = accept(servSock, (struct sockaddr *) &echoClntAddr, &clntLen);
    
    if (clntSock < 0 )
    {
       printf("Error in accpet\n");
       exit(1);
    }
    
    /* recv here if everything is okey */
    Last edited by nkhambal; 09-03-2005 at 02:07 PM.

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