Do not release TCP sockets while still in use

SDLNet_TCP_Close() not only closes, but also release the resources.

Therefore, we must not close the socket if another thread attempts to
read it.

For that purpose, move socket closing from server_stop() to
server_destroy().

app/src/scrcpy.c

@@ -99,13 +99,16 @@ SDL_bool scrcpy(const char *serial, Uint16 local_port, Uint16 max_size, Uint32 b
         return SDL_FALSE;
     }
 
+    SDL_bool ret = SDL_TRUE;
+
     // to reduce startup time, we could be tempted to init other stuff before blocking here
     // but we should not block after SDL_Init since it handles the signals (Ctrl+C) in its
     // event loop: blocking could lead to deadlock
     TCPsocket device_socket = server_connect_to(&server, serial);
     if (!device_socket) {
         server_stop(&server, serial);
-        return SDL_FALSE;
+        ret = SDL_FALSE;
+        goto finally_destroy_server;
     }
 
     char device_name[DEVICE_NAME_FIELD_LENGTH];
@@ -116,16 +119,16 @@ SDL_bool scrcpy(const char *serial, Uint16 local_port, Uint16 max_size, Uint32 b
     // to init the window immediately
     if (!device_read_info(device_socket, device_name, &frame_size)) {
         server_stop(&server, serial);
-        return SDL_FALSE;
+        ret = SDL_FALSE;
+        goto finally_destroy_server;
     }
 
     if (!frames_init(&frames)) {
         server_stop(&server, serial);
-        return SDL_FALSE;
+        ret = SDL_FALSE;
+        goto finally_destroy_server;
     }
 
-    SDL_bool ret = SDL_TRUE;
-
     decoder.frames = &frames;
     decoder.video_socket = device_socket;
 
@@ -173,6 +176,8 @@ finally_stop_decoder:
     decoder_join(&decoder);
 finally_destroy_frames:
     frames_destroy(&frames);
+finally_destroy_server:
+    server_destroy(&server);
 
     return ret;
 }

app/src/server.c

@@ -115,13 +115,6 @@ TCPsocket server_connect_to(struct server *server, const char *serial) {
 
 void server_stop(struct server *server, const char *serial) {
     SDL_assert(server->process != PROCESS_NONE);
-    if (server->server_socket) {
-        SDLNet_TCP_Close(server->server_socket);
-    }
-    if (server->device_socket) {
-        SDLNet_TCP_Close(server->device_socket);
-    }
-
     terminate_server(server->process);
 
     if (server->adb_reverse_enabled) {
@@ -129,3 +122,12 @@ void server_stop(struct server *server, const char *serial) {
         disable_tunnel(serial);
     }
 }
+
+void server_destroy(struct server *server) {
+    if (server->server_socket) {
+        SDLNet_TCP_Close(server->server_socket);
+    }
+    if (server->device_socket) {
+        SDLNet_TCP_Close(server->device_socket);
+    }
+}

app/src/server.h

@@ -31,4 +31,7 @@ TCPsocket server_connect_to(struct server *server, const char *serial);
 // disconnect and kill the server process
 void server_stop(struct server *server, const char *serial);
 
+// close and release sockets
+void server_destroy(struct server *server);
+
 #endif