Error in the Client Program

[dranz3r]

I wrote this c program to send a struct from the client to a server which has the same struct initialized in it. I used gcc feature of cygwin to compile it and I got the following error. Can anyone tell me wha could possibly have gone wrong because I was not able to figure out anything.

348 [main] c 7160 _cygtls::handle_exceptions: Error while dumping state (probably corrupted stack)      
Segmentation fault (core dumped)  
 

#include <stdio.h>    /* standard C i/o facilities */
#include <stdlib.h>    /* needed for atoi() */
#include <unistd.h>    /* Unix System Calls */
#include <sys/types.h>    /* system data type definitions */
#include <sys/socket.h> /* socket specific definitions */
#include <netinet/in.h> /* INET constants and stuff */
#include <arpa/inet.h>    /* IP address conversion stuff */
#include <netdb.h>    /* Name lookups (gethostbyname) */
#include <fcntl.h>      /* Read and Write Fucntions */
#include <string.h>     /* FoR Memset() */
 
 
void DieWithError(char *errorMessage)
{
    perror(errorMessage);
    exit(1);
}
 
 
struct message
{
       int packet_num;
       int syn;
       int ack;
       char * msg;
};
 
int main(int argc, char *argv[])
{
    int sock;
    int fd;
    int x;
    int packet_count;
    struct sockaddr_in echoServAddr;
    struct sockaddr_in fromAddr;
    unsigned short echoServPort;
    unsigned int fromSize;
    char *servIP;
    char *buff;
    struct message recvMsg;
    struct message sendMsg;
    struct message sendMsgBuff;
    int stringLen;
 
    if((argc < 3 ) || ( argc > 4 ))
    {
             fprintf(stderr,"Usage: %s <Server IP> <File name> [<Port Number>]\n",argv[0]);
             exit(1);
             }
    servIP = argv[1];
 
    if(argc == 4)
                      echoServPort = atoi(argv[3]);
    else
                      echoServPort = 7;
 
 
    /* Create a datagram/UDP socket */
    if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
        DieWithError("socket() failed");
 
    memset(&echoServAddr, 0, sizeof(echoServAddr));
    memset(&recvMsg,0,sizeof(recvMsg));
    memset(&sendMsg,0,sizeof(sendMsg));
    echoServAddr.sin_family = AF_INET;
    echoServAddr.sin_addr.s_addr = inet_addr(servIP);
    echoServAddr.sin_port = htons(echoServPort);
 
    fd = open(argv[2],O_RDONLY);
    if(fd==-1)
        DieWithError("File opening failed");
 
    buff = (char*)(malloc(10000));    
    x = read(fd,buff,sizeof(buff));
    if(x==-1)
        DieWithError("File read failed");
 
    packet_count=0;
 
    sendMsg.packet_num = htonl(packet_count);
    sendMsg.syn = 0;
    sendMsg.ack = 1;
    buff = argv[2];
    buff[strlen(buff) + 1] = '\0';
    sendMsg.msg = buff;
 
    /* Send the string to the server */
    if((sendto(sock, (struct  message *) &sendMsg, sizeof(sendMsg), 0, (struct sockaddr *) &echoServAddr, sizeof(echoServAddr))) != sizeof(sendMsg))
                     DieWithError("sendto() sent a different number of bytes than expected");
 
    /* Recv a response */
    fromSize = sizeof(fromAddr);
    if(stringLen = recvfrom(sock, (struct  message *) &recvMsg, sizeof(recvMsg), 0, (struct sockaddr*) &fromAddr, &fromSize) != sizeof(sendMsg))
                      DieWithError("recvfrom() failed");
 
    if(recvMsg.ack != sendMsg.ack)
                      DieWithError("Message Not Acknowledged properly");
 
    if (echoServAddr.sin_addr.s_addr != fromAddr.sin_addr.s_addr)
    {
        fprintf(stderr,"Error: received a packet from unknown source.\n");
        exit(1);
    }
 
    /* null-terminate the received data */
    printf("Received Acknowledgement : %s\n", recvMsg.ack);
 
    close(sock);
    exit(0);
}
 

[donbock]

Can you use a debugger to find out whereabouts in your program the error occurs? If not, sprinkle printf's throughout your program and look to see the last printf message before the error message.