Initial commit

knock_client.c

@@ -0,0 +1,95 @@
+// Simple TCP knock client - sends single SYN packets without retries
+// Compile: cl /W4 /O2 knock_client.c /ws2_32.lib
+
+#include <winsock2.h>
+#include <ws2tcpip.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#pragma comment(lib, "ws2_32.lib")
+
+void knock_port(const char* ip, int port) {
+    SOCKET s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
+    if (s == INVALID_SOCKET) {
+        printf("socket failed: %d\n", WSAGetLastError());
+        return;
+    }
+
+    // Set socket to close immediately after connect attempt
+    BOOL dontlinger = FALSE;
+    setsockopt(s, SOL_SOCKET, SO_DONTLINGER, (char*)&dontlinger, sizeof(dontlinger));
+
+    struct sockaddr_in addr;
+    memset(&addr, 0, sizeof(addr));
+    addr.sin_family = AF_INET;
+    addr.sin_port = htons((unsigned short)port);
+    inet_pton(AF_INET, ip, &addr.sin_addr);
+
+    printf("Knocking on port %d...\n", port);
+    
+    // Connect will send SYN, and we close immediately after
+    int result = connect(s, (struct sockaddr*)&addr, sizeof(addr));
+    
+    // Give it a moment to send the packet
+    Sleep(100);
+    
+    // Close immediately without retrying
+    closesocket(s);
+    
+    if (result == SOCKET_ERROR) {
+        printf("  Connection refused (expected - no listener)\n");
+    } else {
+        printf("  Connected!\n");
+    }
+}
+
+int main(int argc, char* argv[]) {
+    if (argc < 2) {
+        printf("Usage: %s <target_ip> [port1 port2 port3 ...]\n", argv[0]);
+        printf("Default ports: 7000 8000 9000\n");
+        return 1;
+    }
+
+    const char* ip = argv[1];
+    
+    int ports[10];
+    int num_ports;
+    
+    if (argc > 2) {
+        num_ports = argc - 2;
+        for (int i = 0; i < num_ports && i < 10; i++) {
+            ports[i] = atoi(argv[i + 2]);
+        }
+    } else {
+        num_ports = 3;
+        ports[0] = 7000;
+        ports[1] = 8000;
+        ports[2] = 9000;
+    }
+
+    WSADATA wsa;
+    if (WSAStartup(MAKEWORD(2, 2), &wsa) != 0) {
+        printf("WSAStartup failed\n");
+        return 1;
+    }
+
+    printf("Knocking on %s: ", ip);
+    for (int i = 0; i < num_ports; i++) {
+        printf("%d ", ports[i]);
+    }
+    printf("\n\n");
+
+    for (int i = 0; i < num_ports; i++) {
+        knock_port(ip, ports[i]);
+        if (i < num_ports - 1) {
+            // Wait between knocks
+            Sleep(500);
+        }
+    }
+
+    printf("\nKnock sequence complete!\n");
+    printf("Now try connecting to port 31337\n");
+
+    WSACleanup();
+    return 0;
+}