Question

I use the code on http://www.abc.se/~m6695/udp.html

the code works fine, I can see that the message is sent and the server receives it. However, When I build the program, I get the following “passing argument 5 of ‘sendto’ from incompatible pointer type [enabled by default]” for the line “if (sendto(s, buf, BUFSIZE, 0, &si_other, slen)==-1){“. I would appreciate if anyone could tell me how to fix. thank you

    #define  MAXSTRINGLENGTH 128
#define BUFSIZE 512

void log_msg_send(char *message, char *next_hop);
    void log_msg_send(char *message, char *next_hop);

int main(int argc, char** argv) {
    char hello[] = "hello bitches";
    char next_hop[]= "192.168.1.178";
    log_msg_send(hello, next_hop);
}

void log_msg_send(char *message, char *next_hop){
    char SRV_IP[16]; 
    strcpy(SRV_IP,  next_hop);

         struct sockaddr_in si_other;
         int s, i, slen=sizeof(si_other);
         char buf[50] ;
         strcpy(buf, message);

        if ((s=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP))==-1){
          fprintf(stderr, "inet_aton() failed\n");
          exit(1);
        }

        memset((char *) &si_other, 0, sizeof(si_other));
        si_other.sin_family = AF_INET;
        si_other.sin_port = htons(33333);
        if (inet_aton(SRV_IP, &si_other.sin_addr)==0) {
          fprintf(stderr, "inet_aton() failed\n");
          exit(1);
        }
          printf("Sending the packet %d\n", i);
          if (sendto(s, buf, BUFSIZE, 0, &si_other, slen)==-1){
          fprintf(stderr, "inet_aton() failed\n");
          exit(1);
        }

        close(s);

}

Answer 1

Quick fix:

sendto(s, buf, BUFSIZE, 0, (struct sockaddr *)&si_other, slen)

This conversion is required because sendto() expects a pointer to struct sockaddr as its fifth argument while your particular socket address type is struct sockaddr_in.