Improve error handling for broken SSH connections

- Added detailed error reporting when socket becomes invalid
- Mark tunnel as inactive when SSH connection is broken
- Enhanced debugging for socket closure detection
- Added errno reporting for connection errors
- Improved error messages to distinguish between different failure modes
- Added proper tunnel state management when connections fail
- Better handling of SSH client disconnections during handshake
- Added mutex protection for tunnel state updates during errors

wssshtools/tunnel.c

@@ -272,9 +272,19 @@ void *forward_tcp_to_ws(void *arg) {
             bytes_read = recv(sock, buffer, sizeof(buffer), 0);
             if (bytes_read <= 0) {
                 if (debug) {
-                    printf("[DEBUG] TCP connection closed or error\n");
+                    if (bytes_read == 0) {
+                        printf("[DEBUG] TCP connection closed by peer (SSH client disconnected)\n");
+                    } else {
+                        printf("[DEBUG] TCP connection error: %s\n", strerror(errno));
+                    }
                     fflush(stdout);
                 }
+                // Mark tunnel as inactive since SSH connection is broken
+                pthread_mutex_lock(&tunnel_mutex);
+                if (active_tunnel) {
+                    active_tunnel->active = 0;
+                }
+                pthread_mutex_unlock(&tunnel_mutex);
                 break;
             }
 
@@ -449,9 +459,14 @@ void handle_tunnel_data(SSL *ssl __attribute__((unused)), const char *request_id
     int socket_flags = fcntl(target_sock, F_GETFL);
     if (socket_flags == -1) {
         if (debug) {
-            printf("[DEBUG] Socket %d is invalid (fcntl failed), ignoring tunnel_data\n", target_sock);
+            printf("[DEBUG] Socket %d is invalid (fcntl failed: %s), SSH connection likely closed\n",
+                   target_sock, strerror(errno));
             fflush(stdout);
         }
+        // Mark tunnel as inactive since SSH connection is broken
+        if (active_tunnel) {
+            active_tunnel->active = 0;
+        }
         pthread_mutex_unlock(&tunnel_mutex);
         return;
     }