Trouble with sending a message over a UDP Socket

Question

I am currently attempting to form a program that allows two programs to communicate using one go between file, acting as a data link layer.

The problem I'm having is that even though my message seems to be sending across the network, the message that is received has some weird garbage text after it, and when it is then passed to the main file, the garbage text is all that is passed, and the message disappears completely. Any pointers in the correct direction are greatly appreciated.

Sending program

main(){

    dlinits("hostname", 43520);
    dlsend("hello");

}

Receiving program

#include <string.h>
char* dlrecv();

main(){
    char* test;
    dlinitr(43520);
    strcpy(test,dlrecv());

    printf("%s\n", test);



}

Data Link program

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
#define BUFMAX 100

static int sk;
static struct sockaddr_in remote;
static struct sockaddr_in local;

dlinits(char* host, int port){//initialize sender

    struct hostent *hp;
    sk = socket(AF_INET, SOCK_DGRAM, 0);

    remote.sin_family = AF_INET;

    hp = gethostbyname(host);
    if (hp == NULL){
        printf("Can't find host name\n");
        exit(1);
    }

    bcopy(hp->h_addr,&remote.sin_addr.s_addr,hp->h_length);

    remote.sin_port = ntohs(port);
}

dlinitr(int port){//initialize receiver
    int rlen = sizeof(remote);
    int len = sizeof(local);
    char buf[BUFMAX];

    sk = socket(AF_INET,SOCK_DGRAM,0);

    local.sin_family = AF_INET;
    local.sin_addr.s_addr = INADDR_ANY;
    local.sin_port = htons(port);
    bind (sk, &local,sizeof(local));

    getsockname(sk,&local,&len);

}

dlsend(char* msg){//send data

    printf("%s\n", msg);
    sendto(sk,msg,sizeof(msg)+1,0,&remote,sizeof(remote));
} 

char* dlrecv(){//receive data
    char* msg[BUFMAX];

    recvfrom(sk,msg,BUFMAX,0,&remote,sizeof(remote));
    printf("%s\n", msg);
    return msg;
}

Ed Heal Ed Heal · Accepted Answer · 2014-03-08T08:36:53

The line

sendto(sk,msg,sizeof(msg)+1,0,&remote,sizeof(remote));

Should be

sendto(sk,msg,strlen(msg)+1,0,&remote,sizeof(remote));

Trouble with sending a message over a UDP Socket

1 Answers