Add Android NetSocket implementation.

Automatically acquire and release multicast lock when needed.

doc/classes/PacketPeerUDP.xml

@@ -47,6 +47,7 @@
 			<description>
 				Joins the multicast group specified by [code]multicast_address[/code] using the interface identified by [code]interface_name[/code].
 				You can join the same multicast group with multiple interfaces. Use [method IP.get_local_interfaces] to know which are available.
+				Note: Some Android devices might require the [code]CHANGE_WIFI_MULTICAST_STATE[/code] permission for multicast to work.
 			</description>
 		</method>
 		<method name="leave_multicast_group">
@@ -83,6 +84,7 @@
 			</argument>
 			<description>
 				Enable or disable sending of broadcast packets (e.g. [code]set_dest_address("255.255.255.255", 4343)[/code]. This option is disabled by default.
+				Note: Some Android devices might require the [code]CHANGE_WIFI_MULTICAST_STATE[/code] permission and this option to be enabled to receive broadcast packets too.
 			</description>
 		</method>
 		<method name="set_dest_address">

platform/android/SCsub

@@ -12,6 +12,7 @@ android_files = [
     'file_access_jandroid.cpp',
     'dir_access_jandroid.cpp',
     'thread_jandroid.cpp',
+    'net_socket_android.cpp',
     'audio_driver_jandroid.cpp',
     'java_godot_lib_jni.cpp',
     'java_class_wrapper.cpp',

platform/android/java_godot_lib_jni.cpp

@@ -43,6 +43,7 @@
 #include "java_class_wrapper.h"
 #include "main/input_default.h"
 #include "main/main.h"
+#include "net_socket_android.h"
 #include "os_android.h"
 #include "string_android.h"
 #include "thread_jandroid.h"
@@ -635,6 +636,7 @@ JNIEXPORT void JNICALL Java_org_godotengine_godot_GodotLib_initialize(JNIEnv *en
 
 	DirAccessJAndroid::setup(godot_io_java->get_instance());
 	AudioDriverAndroid::setup(godot_io_java->get_instance());
+	NetSocketAndroid::setup(godot_java->get_member_object("netUtils", "Lorg/godotengine/godot/utils/GodotNetUtils;", env));
 
 	os_android = new OS_Android(godot_java, godot_io_java, p_use_apk_expansion);
 

platform/android/net_socket_android.cpp

@@ -0,0 +1,136 @@
+/*************************************************************************/
+/*  net_socket_android.cpp                                               */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2019 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2019 Godot Engine contributors (cf. AUTHORS.md)    */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+#include "net_socket_android.h"
+
+#include "thread_jandroid.h"
+
+jobject NetSocketAndroid::net_utils = 0;
+jclass NetSocketAndroid::cls = 0;
+jmethodID NetSocketAndroid::_multicast_lock_acquire = 0;
+jmethodID NetSocketAndroid::_multicast_lock_release = 0;
+
+void NetSocketAndroid::setup(jobject p_net_utils) {
+
+	JNIEnv *env = ThreadAndroid::get_env();
+
+	net_utils = env->NewGlobalRef(p_net_utils);
+
+	jclass c = env->GetObjectClass(net_utils);
+	cls = (jclass)env->NewGlobalRef(c);
+
+	_multicast_lock_acquire = env->GetMethodID(cls, "multicastLockAcquire", "()V");
+	_multicast_lock_release = env->GetMethodID(cls, "multicastLockRelease", "()V");
+}
+
+void NetSocketAndroid::multicast_lock_acquire() {
+	if (_multicast_lock_acquire) {
+		JNIEnv *env = ThreadAndroid::get_env();
+		env->CallVoidMethod(net_utils, _multicast_lock_acquire);
+	}
+}
+
+void NetSocketAndroid::multicast_lock_release() {
+	if (_multicast_lock_release) {
+		JNIEnv *env = ThreadAndroid::get_env();
+		env->CallVoidMethod(net_utils, _multicast_lock_release);
+	}
+}
+
+NetSocket *NetSocketAndroid::_create_func() {
+	return memnew(NetSocketAndroid);
+}
+
+void NetSocketAndroid::make_default() {
+	_create = _create_func;
+}
+
+NetSocketAndroid::NetSocketAndroid() :
+		wants_broadcast(false),
+		multicast_groups(0) {
+}
+
+NetSocketAndroid::~NetSocketAndroid() {
+	close();
+}
+
+void NetSocketAndroid::close() {
+	NetSocketPosix::close();
+	if (wants_broadcast)
+		multicast_lock_release();
+	if (multicast_groups)
+		multicast_lock_release();
+	wants_broadcast = false;
+	multicast_groups = 0;
+}
+
+Error NetSocketAndroid::set_broadcasting_enabled(bool p_enabled) {
+	Error err = NetSocketPosix::set_broadcasting_enabled(p_enabled);
+	if (err != OK)
+		return err;
+
+	if (p_enabled != wants_broadcast) {
+		if (p_enabled) {
+			multicast_lock_acquire();
+		} else {
+			multicast_lock_release();
+		}
+
+		wants_broadcast = p_enabled;
+	}
+
+	return OK;
+}
+
+Error NetSocketAndroid::join_multicast_group(const IP_Address &p_multi_address, String p_if_name) {
+	Error err = NetSocketPosix::join_multicast_group(p_multi_address, p_if_name);
+	if (err != OK)
+		return err;
+
+	if (!multicast_groups)
+		multicast_lock_acquire();
+	multicast_groups++;
+
+	return OK;
+}
+
+Error NetSocketAndroid::leave_multicast_group(const IP_Address &p_multi_address, String p_if_name) {
+	Error err = NetSocketPosix::leave_multicast_group(p_multi_address, p_if_name);
+	if (err != OK)
+		return err;
+
+	ERR_FAIL_COND_V(multicast_groups == 0, ERR_BUG);
+
+	multicast_groups--;
+	if (!multicast_groups)
+		multicast_lock_release();
+
+	return OK;
+}

platform/android/net_socket_android.h

@@ -0,0 +1,78 @@
+/*************************************************************************/
+/*  net_socket_android.h                                                 */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2019 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2019 Godot Engine contributors (cf. AUTHORS.md)    */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+#ifndef NET_SOCKET_ANDROID_H
+#define NET_SOCKET_ANDROID_H
+
+#include "drivers/unix/net_socket_posix.h"
+
+#include <jni.h>
+
+/**
+ * Specialized NetSocket implementation for Android.
+ *
+ * Some devices requires Android-specific code to acquire a MulticastLock
+ * before sockets are allowed to receive broadcast and multicast packets.
+ * This implementation calls into Java code and automatically acquire/release
+ * the lock when broadcasting is enabled/disabled on a socket, or that socket
+ * joins/leaves a multicast group.
+ */
+class NetSocketAndroid : public NetSocketPosix {
+
+private:
+	static jobject net_utils;
+	static jclass cls;
+	static jmethodID _multicast_lock_acquire;
+	static jmethodID _multicast_lock_release;
+
+	bool wants_broadcast;
+	int multicast_groups;
+
+	static void multicast_lock_acquire();
+	static void multicast_lock_release();
+
+protected:
+	static NetSocket *_create_func();
+
+public:
+	static void make_default();
+	static void setup(jobject p_net_utils);
+
+	virtual void close();
+
+	virtual Error set_broadcasting_enabled(bool p_enabled);
+	virtual Error join_multicast_group(const IP_Address &p_multi_address, String p_if_name);
+	virtual Error leave_multicast_group(const IP_Address &p_multi_address, String p_if_name);
+
+	NetSocketAndroid();
+	~NetSocketAndroid();
+};
+
+#endif

platform/android/os_android.cpp

@@ -43,6 +43,7 @@
 
 #include "dir_access_jandroid.h"
 #include "file_access_jandroid.h"
+#include "net_socket_android.h"
 
 #include <dlfcn.h>
 
@@ -106,6 +107,8 @@ void OS_Android::initialize_core() {
 		DirAccess::make_default<DirAccessJAndroid>(DirAccess::ACCESS_RESOURCES);
 	DirAccess::make_default<DirAccessUnix>(DirAccess::ACCESS_USERDATA);
 	DirAccess::make_default<DirAccessUnix>(DirAccess::ACCESS_FILESYSTEM);
+
+	NetSocketAndroid::make_default();
 }
 
 void OS_Android::set_opengl_extensions(const char *p_gl_extensions) {