stripped example taken from one of my PoC compatible with both Windows and Linux.
/*
by Luigi Auriemma
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#ifdef WIN32
#include <winsock.h>
#include "winerr.h"
#define close closesocket
#define sleep Sleep
#define ONESEC 1000
#else
#include <unistd.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netdb.h>
#define ONESEC 1
#define stristr strcasestr
#define stricmp strcasecmp
#endif
typedef unsigned char u8;
typedef unsigned short u16;
typedef unsigned int u32;
#define PORT 1234
#define BUFFSZ 1500
int send_recv(int sd, u8 *in, int insz, u8 *out, int outsz, struct sockaddr_in *peer, int err);
int udp_sock(void);
int timeout(int sock, int secs);
u32 resolv(char *host);
void std_err(void);
int main(int argc, char *argv[]) {
struct sockaddr_in peer;
int sd,
len;
u16 port = PORT;
u8 buff[BUFFSZ],
*host;
#ifdef WIN32
WSADATA wsadata;
WSAStartup(MAKEWORD(1,0), &wsadata);
#endif
if(argc < 2) {
printf("\n"
"Usage: %s <host> [port(%d)]\n"
"\n", argv[0], port);
exit(1);
}
host = argv[1];
if(argc > 2) port = atoi(argv[2]);
peer.sin_addr.s_addr = resolv(host);
peer.sin_port = htons(port);
peer.sin_family = AF_INET;
printf("- target %s : %hu\n", inet_ntoa(peer.sin_addr), ntohs(peer.sin_port));
sd = udp_sock();
len = send_recv(sd, "mypacket", 8, buff, BUFFSZ, &peer, 1);
printf("- received data: %s\n", buff);
close(sd);
return(0);
}
int send_recv(int sd, u8 *in, int insz, u8 *out, int outsz, struct sockaddr_in *peer, int err) {
int retry,
len;
if(in && !out) {
//fputc('.', stdout);
if(sendto(sd, in, insz, 0, (struct sockaddr *)peer, sizeof(struct sockaddr_in))
< 0) goto quit;
return(0);
}
if(in) {
for(retry = 2; retry; retry--) {
//fputc('.', stdout);
if(sendto(sd, in, insz, 0, (struct sockaddr *)peer, sizeof(struct sockaddr_in))
< 0) goto quit;
if(!timeout(sd, 1)) break;
}
if(!retry) goto quit2;
} else {
if(timeout(sd, 3) < 0) goto quit2;
}
//fputc('.', stdout);
len = recvfrom(sd, out, outsz, 0, NULL, NULL);
if(len < 0) goto quit;
return(len);
quit:
if(err) std_err();
return(-1);
quit2:
if(err) {
printf("\nError: socket timeout, no reply received\n\n");
exit(1);
}
return(-1);
}
int udp_sock(void) {
struct linger ling = {1,1};
int sd;
sd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if(sd < 0) std_err();
setsockopt(sd, SOL_SOCKET, SO_LINGER, (char *)&ling, sizeof(ling));
return(sd);
}
int timeout(int sock, int secs) {
struct timeval tout;
fd_set fd_read;
tout.tv_sec = secs;
tout.tv_usec = 0;
FD_ZERO(&fd_read);
FD_SET(sock, &fd_read);
if(select(sock + 1, &fd_read, NULL, NULL, &tout)
<= 0) return(-1);
return(0);
}
u32 resolv(char *host) {
struct hostent *hp;
u32 host_ip;
host_ip = inet_addr(host);
if(host_ip == INADDR_NONE) {
hp = gethostbyname(host);
if(!hp) {
printf("\nError: Unable to resolv hostname (%s)\n", host);
exit(1);
} else host_ip = *(u32 *)hp->h_addr;
}
return(host_ip);
}
#ifndef WIN32
void std_err(void) {
perror("\nError");
exit(1);
}
#endif
