Mehrdad Mehrdad - 9 months ago 61
C Question

Why is my socket's open port not listed by netstat?

If you run this example, you'll see the port is never listed by

. Why? And how do I make it so?

#include <WinSock.h>
#include <io.h>
#include <stdio.h>

#pragma comment(lib, "WS2_32")

int main() {
WORD wVers = MAKEWORD(2, 2);
WSAStartup(wVers, &wsa);
SOCKET sock = socket(AF_INET, SOCK_STREAM, 6);
if (sock != INVALID_SOCKET) {
struct sockaddr_in addr = { 0 };
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
int addrlen = sizeof(addr);
bind(sock, (struct sockaddr *)&addr, addrlen);
if (getsockname(sock, (struct sockaddr *)&addr, &addrlen) == 0) {
fprintf(stdout, "HANDLE = %d, port = %d\n", sock, addr.sin_port);
system("netstat -a -n");

Answer Source

netstat -a only lists connected sockets and listening socket.

  -a            Displays all connections and listening ports.

Neither connect nor listen was called on your socket, so it falls outside the purview of netstat -a.

However, since Windows 10, you can use netstat -q.

  -q            Displays all connections, listening ports, and bound