Core: Add UNIX domain socket support

> [!NOTE]
>
> Later versions of Windows has support for `AF_UNIX`, so it could be
> added.

core/debugger/engine_debugger.cpp

@@ -121,7 +121,10 @@ void EngineDebugger::iteration(uint64_t p_frame_ticks, uint64_t p_process_ticks,
 }
 
 void EngineDebugger::initialize(const String &p_uri, bool p_skip_breakpoints, bool p_ignore_error_breaks, const Vector<String> &p_breakpoints, void (*p_allow_focus_steal_fn)()) {
-	register_uri_handler("tcp://", RemoteDebuggerPeerTCP::create); // TCP is the default protocol. Platforms/modules can add more.
+	register_uri_handler("tcp://", RemoteDebuggerPeerTCP::create_tcp); // TCP is the default protocol. Platforms/modules can add more.
+#ifdef UNIX_ENABLED
+	register_uri_handler("unix://", RemoteDebuggerPeerTCP::create_unix);
+#endif
 	if (p_uri.is_empty()) {
 		return;
 	}
@@ -132,10 +135,10 @@ void EngineDebugger::initialize(const String &p_uri, bool p_skip_breakpoints, bo
 		OS::get_singleton()->initialize_debugging();
 	} else if (p_uri.contains("://")) {
 		const String proto = p_uri.substr(0, p_uri.find("://") + 3);
-		if (!protocols.has(proto)) {
-			return;
-		}
-		RemoteDebuggerPeer *peer = protocols[proto](p_uri);
+		CreatePeerFunc *create_fn = protocols.getptr(proto);
+		ERR_FAIL_NULL_MSG(create_fn, vformat("Invalid protocol: %s.", proto));
+
+		RemoteDebuggerPeer *peer = (*create_fn)(p_uri);
 		if (!peer) {
 			return;
 		}

core/debugger/remote_debugger_peer.cpp

@@ -76,18 +76,19 @@ void RemoteDebuggerPeerTCP::close() {
 	in_buf.clear();
 }
 
-RemoteDebuggerPeerTCP::RemoteDebuggerPeerTCP(Ref<StreamPeerTCP> p_tcp) {
+RemoteDebuggerPeerTCP::RemoteDebuggerPeerTCP() {
 	// This means remote debugger takes 16 MiB just because it exists...
 	in_buf.resize((8 << 20) + 4); // 8 MiB should be way more than enough (need 4 extra bytes for encoding packet size).
 	out_buf.resize(8 << 20); // 8 MiB should be way more than enough
-	tcp_client = p_tcp;
-	if (tcp_client.is_valid()) { // Attaching to an already connected stream.
-		connected = true;
-		running = true;
-		thread.start(_thread_func, this);
-	} else {
-		tcp_client.instantiate();
-	}
+}
+
+RemoteDebuggerPeerTCP::RemoteDebuggerPeerTCP(Ref<StreamPeerSocket> p_stream) :
+		RemoteDebuggerPeerTCP() {
+	DEV_ASSERT(p_stream.is_valid());
+	tcp_client = p_stream;
+	connected = true;
+	running = true;
+	thread.start(_thread_func, this);
 }
 
 RemoteDebuggerPeerTCP::~RemoteDebuggerPeerTCP() {
@@ -154,22 +155,10 @@ void RemoteDebuggerPeerTCP::_read_in() {
 	}
 }
 
-Error RemoteDebuggerPeerTCP::connect_to_host(const String &p_host, uint16_t p_port) {
-	IPAddress ip;
-	if (p_host.is_valid_ip_address()) {
-		ip = p_host;
-	} else {
-		ip = IP::get_singleton()->resolve_hostname(p_host);
-	}
-
-	int port = p_port;
-
+Error RemoteDebuggerPeerTCP::_try_connect(Ref<StreamPeerSocket> tcp_client) {
 	const int tries = 6;
 	const int waits[tries] = { 1, 10, 100, 1000, 1000, 1000 };
 
-	Error err = tcp_client->connect_to_host(ip, port);
-	ERR_FAIL_COND_V_MSG(err != OK, err, vformat("Remote Debugger: Unable to connect to host '%s:%d'.", p_host, port));
-
 	for (int i = 0; i < tries; i++) {
 		tcp_client->poll();
 		if (tcp_client->get_status() == StreamPeerTCP::STATUS_CONNECTED) {
@@ -186,9 +175,6 @@ Error RemoteDebuggerPeerTCP::connect_to_host(const String &p_host, uint16_t p_po
 		ERR_PRINT(vformat("Remote Debugger: Unable to connect. Status: %s.", String::num_int64(tcp_client->get_status())));
 		return FAILED;
 	}
-	connected = true;
-	running = true;
-	thread.start(_thread_func, this);
 	return OK;
 }
 
@@ -222,7 +208,7 @@ void RemoteDebuggerPeerTCP::_poll() {
 	}
 }
 
-RemoteDebuggerPeer *RemoteDebuggerPeerTCP::create(const String &p_uri) {
+RemoteDebuggerPeer *RemoteDebuggerPeerTCP::create_tcp(const String &p_uri) {
 	ERR_FAIL_COND_V(!p_uri.begins_with("tcp://"), nullptr);
 
 	String debug_host = p_uri.replace("tcp://", "");
@@ -234,13 +220,30 @@ RemoteDebuggerPeer *RemoteDebuggerPeerTCP::create(const String &p_uri) {
 		debug_host = debug_host.substr(0, sep_pos);
 	}
 
-	RemoteDebuggerPeerTCP *peer = memnew(RemoteDebuggerPeerTCP);
-	Error err = peer->connect_to_host(debug_host, debug_port);
-	if (err != OK) {
-		memdelete(peer);
-		return nullptr;
+	IPAddress ip;
+	if (debug_host.is_valid_ip_address()) {
+		ip = debug_host;
+	} else {
+		ip = IP::get_singleton()->resolve_hostname(debug_host);
 	}
-	return peer;
+
+	Ref<StreamPeerTCP> stream;
+	stream.instantiate();
+	ERR_FAIL_COND_V_MSG(stream->connect_to_host(ip, debug_port) != OK, nullptr, vformat("Remote Debugger: Unable to connect to host '%s:%d'.", debug_host, debug_port));
+	ERR_FAIL_COND_V(_try_connect(stream), nullptr);
+	return memnew(RemoteDebuggerPeerTCP(stream));
+}
+
+RemoteDebuggerPeer *RemoteDebuggerPeerTCP::create_unix(const String &p_uri) {
+	ERR_FAIL_COND_V(!p_uri.begins_with("unix://"), nullptr);
+
+	String debug_path = p_uri.replace("unix://", "");
+	Ref<StreamPeerUDS> stream;
+	stream.instantiate();
+	Error err = stream->connect_to_host(debug_path);
+	ERR_FAIL_COND_V_MSG(err != OK && err != ERR_BUSY, nullptr, vformat("Remote Debugger: Unable to connect to socket path '%s'.", debug_path));
+	ERR_FAIL_COND_V(_try_connect(stream), nullptr);
+	return memnew(RemoteDebuggerPeerTCP(stream));
 }
 
 RemoteDebuggerPeer::RemoteDebuggerPeer() {

core/debugger/remote_debugger_peer.h

@@ -31,6 +31,7 @@
 #pragma once
 
 #include "core/io/stream_peer_tcp.h"
+#include "core/io/stream_peer_uds.h"
 #include "core/object/ref_counted.h"
 #include "core/os/mutex.h"
 #include "core/os/thread.h"
@@ -59,7 +60,7 @@ class RemoteDebuggerPeerTCP : public RemoteDebuggerPeer {
 	GDSOFTCLASS(RemoteDebuggerPeerTCP, RemoteDebuggerPeer);
 
 private:
-	Ref<StreamPeerTCP> tcp_client;
+	Ref<StreamPeerSocket> tcp_client;
 	Mutex mutex;
 	Thread thread;
 	List<Array> in_queue;
@@ -78,11 +79,11 @@ private:
 	void _poll();
 	void _write_out();
 	void _read_in();
+	static Error _try_connect(Ref<StreamPeerSocket> p_stream);
 
 public:
-	static RemoteDebuggerPeer *create(const String &p_uri);
-
-	Error connect_to_host(const String &p_host, uint16_t p_port);
+	static RemoteDebuggerPeer *create_tcp(const String &p_uri);
+	static RemoteDebuggerPeer *create_unix(const String &p_uri);
 
 	bool is_peer_connected() override;
 	int get_max_message_size() const override;
@@ -92,6 +93,7 @@ public:
 	void poll() override;
 	void close() override;
 
-	RemoteDebuggerPeerTCP(Ref<StreamPeerTCP> p_stream = Ref<StreamPeerTCP>());
+	RemoteDebuggerPeerTCP(Ref<StreamPeerSocket> p_stream);
+	RemoteDebuggerPeerTCP();
 	~RemoteDebuggerPeerTCP();
 };