#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <ctype.h>
#include <netdb.h>
#include <netinet/in.h>

/*
	Translate an IP number (ascii) into four number
	Return -1 if the IP number is invalid.
*/
static int ipnum_aip24 (const char *aip, int num4[4])
{
	int ret = 0;
	for (int i=0; i<4; i++){
		if (!isdigit(aip[0])){
			ret = -1;
			break;
		}else{
			int no = num4[i] = atoi(aip);
			if (no < 0 || no > 255) ret = -1;
			while (isdigit(*aip)) aip++;
			if (i < 3){
				if (*aip != '.'){
					ret = -1;
					break;
				}
				aip++;
			}
		}
	}
	if (*aip != '\0' && !isspace(*aip)) ret = -1;
	return ret;
}

/*
	Check is a string is valid IP number.
	if (ishost), check if the IP is not a broadcast or a network address.
*/
static bool ipnum_validip(const char *aip, bool ishost)
{
	int num4[4];
	bool ret = false;
	if (ipnum_aip24(aip,num4) != -1){
		ret = true;
		if (ishost && (num4[3] == 0 || num4[3] == 255)){
			ret = false;
		}
	}
	return ret;
}
/*
	Compute an IP number from a string.
*/
static unsigned long ipnum_aip2l (const char *aip)
{
	unsigned long ret = 0xffffffffl;
	int n[4];
	if (ipnum_aip24(aip,n) != -1){
		ret = (n[0] << 24) + (n[1] << 16) + (n[2] << 8) + n[3];
	}
	return ret;
}

static int repeat_sinconnect (struct sockaddr_in &sin, int nbretry)
{
	int ret = -1;
	for (int i=0; i<nbretry; i++){		
		int s;
		if ((s = socket (AF_INET, SOCK_DGRAM, 0)) >= 0) {
			fprintf (stderr,"avantconnect %d\n",s);
			if (connect (s, (struct sockaddr *) &sin, sizeof (sin))
				== -1){
				if (i==0){
					fprintf (stderr,"Can't connect %d(%s)\n",errno
						,strerror(errno));
				}
				close (s);
				sleep(1);
			}else{
				ret = s;
				break;
			}
		}else{
			fprintf (stderr,"Can't build the socket %d(%s)\n",errno
				,strerror(errno));
		}
	}
	return ret;
}



static int repeat_connect (const char *servname, int port)
{
	int ret = -1;
	struct sockaddr_in sin;
	sin.sin_family = AF_INET;
	sin.sin_port = htons(port);
	if (ipnum_validip (servname,true)){
		long addr = htonl(ipnum_aip2l (servname));
		memcpy  (&sin.sin_addr,&addr, sizeof(addr));
		ret = repeat_sinconnect (sin,3);
	}else{
		struct hostent	*h = (struct hostent *) gethostbyname(servname);
		if (h == NULL){
			fprintf (stderr,"No server \"%s\" defined",servname);
		}else{
			memcpy  (&sin.sin_addr,h->h_addr, h->h_length);
			ret = repeat_sinconnect (sin,3);
		}
	}
	return ret;
}

static int repeat_setlisten (int port)
{
	int listen_handle = socket (AF_INET, SOCK_DGRAM, 0);
	struct sockaddr_in sin;
	sin.sin_family = AF_INET;
	sin.sin_addr.s_addr = INADDR_ANY;
	sin.sin_port = htons(port);
	if (listen_handle == -1){
		fprintf (stderr,"listen_handle %d(%s)\n"
			,errno,strerror(errno));
	#if 0
		int opt = 1;
		}else if (reuseadr
			&& setsockopt(listen_handle,SOL_SOCKET,SO_REUSEADDR,&opt,sizeof(opt))==-1){
						fprintf (stderr,"Can't set socket option SO_REUSEADDR (%s)\n"
							,strerror (errno));
	#endif
	}else if (bind (listen_handle,(struct sockaddr *) &sin, sizeof (sin)) == -1){
		fprintf (stderr,"bind %d(%s)\n",errno,strerror(errno));
	}else if (listen (listen_handle,5) == -1){
		fprintf (stderr,"listen %d(%s)\n",errno,strerror(errno));
	}else{
		printf ("bind ok\n");
	}
	return listen_handle;
}

static void usage ()
{
	fprintf (stderr,"repeat local_port remote_host remote_port\n");
}

int main (int argc, char *argv[])
{
	if (argc != 4){
		usage();
	}else{
		int fdin = repeat_setlisten (atoi(argv[1]));
		int fdout = repeat_connect (argv[2],atoi(argv[3]));
		//printf ("fdin = %d, fdout = %d\n",fdin,fdout);
		while (1){
			char buf[10000];
			//int n = read (fdin,buf,sizeof(buf));
			struct sockaddr from;
			int len;
			int n = recvfrom (fdin,buf,sizeof(buf),0,&from,&len);
			if (n > 0){
				write (fdout,buf,n);
			}else{
				fprintf(stderr,"erreur %d %d (%s)\n",n,errno,strerror(errno));
			}
		}
	}
	return 0;
}