UDP sockets broadcast is now disabled by default.

Add method `set_broadcast_enabled` to allow enabling broadcast via
GDScript.

core/io/packet_peer_udp.cpp

@@ -37,6 +37,12 @@ void PacketPeerUDP::set_blocking_mode(bool p_enable) {
 	blocking = p_enable;
 }
 
+void PacketPeerUDP::set_broadcast_enabled(bool p_enabled) {
+	broadcast = p_enabled;
+	if (_sock.is_valid() && _sock->is_open())
+		_sock->set_broadcasting_enabled(p_enabled);
+}
+
 Error PacketPeerUDP::join_multicast_group(IP_Address p_multi_address, String p_if_name) {
 
 	ERR_FAIL_COND_V(!_sock.is_valid(), ERR_UNAVAILABLE);
@@ -47,6 +53,7 @@ Error PacketPeerUDP::join_multicast_group(IP_Address p_multi_address, String p_i
 		Error err = _sock->open(NetSocket::TYPE_UDP, ip_type);
 		ERR_FAIL_COND_V(err != OK, err);
 		_sock->set_blocking_enabled(false);
+		_sock->set_broadcasting_enabled(broadcast);
 	}
 	return _sock->join_multicast_group(p_multi_address, p_if_name);
 }
@@ -122,6 +129,7 @@ Error PacketPeerUDP::put_packet(const uint8_t *p_buffer, int p_buffer_size) {
 		err = _sock->open(NetSocket::TYPE_UDP, ip_type);
 		ERR_FAIL_COND_V(err != OK, err);
 		_sock->set_blocking_enabled(false);
+		_sock->set_broadcasting_enabled(broadcast);
 	}
 
 	do {
@@ -165,6 +173,7 @@ Error PacketPeerUDP::listen(int p_port, const IP_Address &p_bind_address, int p_
 
 	_sock->set_blocking_enabled(false);
 	_sock->set_reuse_address_enabled(true);
+	_sock->set_broadcasting_enabled(broadcast);
 	err = _sock->bind(p_bind_address, p_port);
 
 	if (err != OK) {
@@ -258,6 +267,7 @@ void PacketPeerUDP::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("get_packet_ip"), &PacketPeerUDP::_get_packet_ip);
 	ClassDB::bind_method(D_METHOD("get_packet_port"), &PacketPeerUDP::get_packet_port);
 	ClassDB::bind_method(D_METHOD("set_dest_address", "host", "port"), &PacketPeerUDP::_set_dest_address);
+	ClassDB::bind_method(D_METHOD("set_broadcast_enabled", "enabled"), &PacketPeerUDP::set_broadcast_enabled);
 	ClassDB::bind_method(D_METHOD("join_multicast_group", "multicast_address", "interface_name"), &PacketPeerUDP::join_multicast_group);
 	ClassDB::bind_method(D_METHOD("leave_multicast_group", "multicast_address", "interface_name"), &PacketPeerUDP::leave_multicast_group);
 }
@@ -267,6 +277,7 @@ PacketPeerUDP::PacketPeerUDP() :
 		queue_count(0),
 		peer_port(0),
 		blocking(true),
+		broadcast(false),
 		_sock(Ref<NetSocket>(NetSocket::create())) {
 	rb.resize(16);
 }

core/io/packet_peer_udp.h

@@ -53,6 +53,7 @@ protected:
 	IP_Address peer_addr;
 	int peer_port;
 	bool blocking;
+	bool broadcast;
 	Ref<NetSocket> _sock;
 
 	static void _bind_methods();
@@ -77,6 +78,7 @@ public:
 	Error get_packet(const uint8_t **r_buffer, int &r_buffer_size);
 	int get_available_packet_count() const;
 	int get_max_packet_size() const;
+	void set_broadcast_enabled(bool p_enabled);
 	Error join_multicast_group(IP_Address p_multi_address, String p_if_name);
 	Error leave_multicast_group(IP_Address p_multi_address, String p_if_name);
 

doc/classes/PacketPeerUDP.xml

@@ -76,6 +76,15 @@
 				If [code]bind_address[/code] is set to any valid address (e.g. [code]"192.168.1.101"[/code], [code]"::1"[/code], etc), the peer will only listen on the interface with that addresses (or fail if no interface with the given address exists).
 			</description>
 		</method>
+		<method name="set_broadcast_enabled">
+			<return type="void">
+			</return>
+			<argument index="0" name="enabled" type="bool">
+			</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.
+			</description>
+		</method>
 		<method name="set_dest_address">
 			<return type="int" enum="Error">
 			</return>
@@ -85,6 +94,7 @@
 			</argument>
 			<description>
 				Sets the destination address and port for sending packets and variables. A hostname will be resolved using DNS if needed.
+				Note: [method set_broadcast_enabled] must be enabled before sending packets to a broadcast address (e.g. [code]255.255.255.255[/code]).
 			</description>
 		</method>
 		<method name="wait">

drivers/unix/net_socket_posix.cpp

@@ -333,9 +333,10 @@ Error NetSocketPosix::open(Type p_sock_type, IP::Type &ip_type) {
 		set_ipv6_only_enabled(ip_type != IP::TYPE_ANY);
 	}
 
-	if (protocol == IPPROTO_UDP && ip_type != IP::TYPE_IPV6) {
-		// Enable broadcasting for UDP sockets if it's not IPv6 only (IPv6 has no broadcast option).
-		set_broadcasting_enabled(true);
+	if (protocol == IPPROTO_UDP) {
+		// Make sure to disable broadcasting for UDP sockets.
+		// Depending on the OS, this option might or might not be enabled by default. Let's normalize it.
+		set_broadcasting_enabled(false);
 	}
 
 	_is_stream = p_sock_type == TYPE_TCP;
@@ -606,7 +607,8 @@ Error NetSocketPosix::sendto(const uint8_t *p_buffer, int p_len, int &r_sent, IP
 Error NetSocketPosix::set_broadcasting_enabled(bool p_enabled) {
 	ERR_FAIL_COND_V(!is_open(), ERR_UNCONFIGURED);
 	// IPv6 has no broadcast support.
-	ERR_FAIL_COND_V(_ip_type == IP::TYPE_IPV6, ERR_UNAVAILABLE);
+	if (_ip_type == IP::TYPE_IPV6)
+		return ERR_UNAVAILABLE;
 
 	int par = p_enabled ? 1 : 0;
 	if (setsockopt(_sock, SOL_SOCKET, SO_BROADCAST, SOCK_CBUF(&par), sizeof(int)) != 0) {