>если сделать надо под *никсы, то имхо проще реализовать это с помощью
>NAT, FireWall и отбражение потров в топку.
Вот реально работающий вариант кода, для перенаправления с одного сокета на другой:
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/time.h>
#include <sys/types.h>
#include <string.h>
#include <signal.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>
static int forward_port;
#undef max
#define max(x,y) ((x) > (y) ? (x) : (y))
static int
listen_socket(int listen_port)
{
struct sockaddr_in a;
int s;
int yes;
if ((s = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
perror("socket");
return -1;
}
yes = 1;
if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR,
(char *) &yes, sizeof(yes)) < 0) {
perror("setsockopt");
close(s);
return -1;
}
memset(&a, 0, sizeof(a));
a.sin_port = htons(listen_port);
a.sin_family = AF_INET;
if (bind(s, (struct sockaddr *) &a, sizeof(a)) < 0) {
perror("bind");
close(s);
return -1;
}
printf("accepting connections on port %d\n", listen_port);
listen(s, 10);
return s;
}
static int
connect_socket(int connect_port, char *address)
{
struct sockaddr_in a;
int s;
if ((s = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
perror("socket");
close(s);
return -1;
}
memset(&a, 0, sizeof(a));
a.sin_port = htons(connect_port);
a.sin_family = AF_INET;
if (!inet_aton(address, (struct in_addr *) &a.sin_addr.s_addr)) {
perror("bad IP address format");
close(s);
return -1;
}
if (connect(s, (struct sockaddr *) &a, sizeof(a)) < 0) {
perror("connect()");
shutdown(s, SHUT_RDWR);
close(s);
return -1;
}
return s;
}
#define SHUT_FD1 { \
if (fd1 >= 0) { \
shutdown(fd1, SHUT_RDWR); \
close(fd1); \
fd1 = -1; \
} \
}
#define SHUT_FD2 { \
if (fd2 >= 0) { \
shutdown(fd2, SHUT_RDWR); \
close(fd2); \
fd2 = -1; \
} \
}
#define BUF_SIZE 1024
int
main(int argc, char **argv)
{
int h;
int fd1 = -1, fd2 = -1;
char buf1[BUF_SIZE], buf2[BUF_SIZE];
int buf1_avail, buf1_written;
int buf2_avail, buf2_written;
if (argc != 4) {
fprintf(stderr,
"Usage\n\tfwd <listen-port> "
"<forward-to-port> <forward-to-ip-address>\n");
exit(EXIT_FAILURE);
}
signal(SIGPIPE, SIG_IGN);
forward_port = atoi(argv[2]);
h = listen_socket(atoi(argv[1]));
if (h < 0)
exit(EXIT_FAILURE);
for (;;) {
int r, nfds = 0;
fd_set rd, wr, er;
FD_ZERO(&rd);
FD_ZERO(&wr);
FD_ZERO(&er);
FD_SET(h, &rd);
nfds = max(nfds, h);
if (fd1 > 0 && buf1_avail < BUF_SIZE) {
FD_SET(fd1, &rd);
nfds = max(nfds, fd1);
}
if (fd2 > 0 && buf2_avail < BUF_SIZE) {
FD_SET(fd2, &rd);
nfds = max(nfds, fd2);
}
if (fd1 > 0
&& buf2_avail - buf2_written > 0) {
FD_SET(fd1, &wr);
nfds = max(nfds, fd1);
}
if (fd2 > 0
&& buf1_avail - buf1_written > 0) {
FD_SET(fd2, &wr);
nfds = max(nfds, fd2);
}
if (fd1 > 0) {
FD_SET(fd1, &er);
nfds = max(nfds, fd1);
}
if (fd2 > 0) {
FD_SET(fd2, &er);
nfds = max(nfds, fd2);
}
r = select(nfds + 1, &rd, &wr, &er, NULL);
if (r == -1 && errno == EINTR)
continue;
if (r < 0) {
perror("select()");
exit(EXIT_FAILURE);
}
if (FD_ISSET(h, &rd)) {
unsigned int l;
struct sockaddr_in client_address;
memset(&client_address, 0, l = sizeof(client_address));
r = accept(h, (struct sockaddr *) &client_address, &l);
if (r < 0) {
perror("accept()");
} else {
SHUT_FD1;
SHUT_FD2;
buf1_avail = buf1_written = 0;
buf2_avail = buf2_written = 0;
fd1 = r;
fd2 =
connect_socket(forward_port, argv[3]);
if (fd2 < 0) {
SHUT_FD1;
} else
printf("connect from %s\n",
inet_ntoa(client_address.sin_addr));
}
}
/* NB: read oob data before normal reads */
if (fd1 > 0)
if (FD_ISSET(fd1, &er)) {
char c;
errno = 0;
r = recv(fd1, &c, 1, MSG_OOB);
if (r < 1) {
SHUT_FD1;
} else
send(fd2, &c, 1, MSG_OOB);
}
if (fd2 > 0)
if (FD_ISSET(fd2, &er)) {
char c;
errno = 0;
r = recv(fd2, &c, 1, MSG_OOB);
if (r < 1) {
SHUT_FD1;
} else
send(fd1, &c, 1, MSG_OOB);
}
if (fd1 > 0)
if (FD_ISSET(fd1, &rd)) {
r =
read(fd1, buf1 + buf1_avail,
BUF_SIZE - buf1_avail);
if (r < 1) {
SHUT_FD1;
} else
buf1_avail += r;
}
if (fd2 > 0)
if (FD_ISSET(fd2, &rd)) {
r =
read(fd2, buf2 + buf2_avail,
BUF_SIZE - buf2_avail);
if (r < 1) {
SHUT_FD2;
} else
buf2_avail += r;
}
if (fd1 > 0)
if (FD_ISSET(fd1, &wr)) {
r =
write(fd1, buf2 + buf2_written,
buf2_avail - buf2_written);
if (r < 1) {
SHUT_FD1;
} else
buf2_written += r;
}
if (fd2 > 0)
if (FD_ISSET(fd2, &wr)) {
r =
write(fd2, buf1 + buf1_written,
buf1_avail - buf1_written);
if (r < 1) {
SHUT_FD2;
} else
buf1_written += r;
}
/* check if write data has caught read data */
if (buf1_written == buf1_avail)
buf1_written = buf1_avail = 0;
if (buf2_written == buf2_avail)
buf2_written = buf2_avail = 0;
/* one side has closed the connection, keep
writing to the other side until empty */
if (fd1 < 0 && buf1_avail - buf1_written == 0) {
SHUT_FD2;
}
if (fd2 < 0 && buf2_avail - buf2_written == 0) {
SHUT_FD1;
}
}
exit(EXIT_SUCCESS);
}
Пользуйтесь ради бога если надо, и мой вам совет -- по чаще заглядывайте в MAN-страницы, там много полезного есть.
PS:
Этот код взят из man 2 select_tut
Советую вам повнимательнее читать маны.
Вариант для распечатки
Программирование под UNIX (Public)
(ok) on 22-Ноя-08, 14:38 
