diff --git a/UDPSocket.cpp b/UDPSocket.cpp
index 967d36f..a8a7fb4 100644
--- a/UDPSocket.cpp
+++ b/UDPSocket.cpp
@@ -63,15 +63,24 @@ CUDPSocket::~CUDPSocket()
 }
 
 int CUDPSocket::lookup(const std::string& hostname, unsigned int port, sockaddr_storage &addr, unsigned int &address_length)
+{
+	struct addrinfo hints;
+
+	::memset(&hints, 0, sizeof(hints));
+
+	return lookup(hostname, port, addr, address_length, hints);
+}
+
+int CUDPSocket::lookup(const std::string& hostname, unsigned int port, sockaddr_storage &addr, unsigned int &address_length, struct addrinfo &hints)
 {
 	int err;
 	std::string portstr = std::to_string(port);
-	struct addrinfo hints, *res;
+	struct addrinfo *res;
 
-	::memset(&hints, 0, sizeof(struct addrinfo));
-	hints.ai_flags = AI_NUMERICSERV;
+	/* port is always digits, no needs to lookup service */
+	hints.ai_flags |= AI_NUMERICSERV;
 
-	err = getaddrinfo(hostname.c_str(), portstr.c_str(), &hints, &res);
+	err = getaddrinfo(hostname.empty() ? NULL : hostname.c_str(), portstr.c_str(), &hints, &res);
 	if (err) {
 		sockaddr_in *paddr = (sockaddr_in *)&addr;
 		::memset(paddr, 0, address_length = sizeof(sockaddr_in));
@@ -88,14 +97,55 @@ int CUDPSocket::lookup(const std::string& hostname, unsigned int port, sockaddr_
 	return 0;
 }
 
+bool CUDPSocket::match(const sockaddr_storage &addr1, const sockaddr_storage &addr2)
+{
+	if (addr1.ss_family != addr2.ss_family)
+		return false;
+
+	switch (addr1.ss_family) {
+	case AF_INET:
+		struct sockaddr_in *in_1, *in_2;
+		in_1 = (struct sockaddr_in *)&addr1;
+		in_2 = (struct sockaddr_in *)&addr2;
+		return ( (in_1->sin_addr.s_addr == in_2->sin_addr.s_addr) &&
+			 (in_1->sin_port == in_2->sin_port) );
+	case AF_INET6:
+		struct sockaddr_in6 *in6_1, *in6_2;
+		in6_1 = (struct sockaddr_in6 *)&addr1;
+		in6_2 = (struct sockaddr_in6 *)&addr2;
+		return ( IN6_ARE_ADDR_EQUAL(&in6_1->sin6_addr, &in6_2->sin6_addr) &&
+			 (in6_1->sin6_port == in6_2->sin6_port) );
+	default:
+		return false;
+	}
+}
+
+bool CUDPSocket::isnone(const sockaddr_storage &addr)
+{
+	struct sockaddr_in *in = (struct sockaddr_in *)&addr;
+
+	return ( (addr.ss_family == AF_INET) &&
+		 (in->sin_addr.s_addr == htonl(INADDR_NONE)) );
+}
+
 bool CUDPSocket::open()
+{
+	return open(AF_UNSPEC);
+}
+
+bool CUDPSocket::open(const unsigned int af)
 {
 	int err;
 	sockaddr_storage addr;
 	unsigned int addrlen;
+	struct addrinfo hints;
+
+	::memset(&hints, 0, sizeof(hints));
+	hints.ai_flags = AI_PASSIVE;
+	hints.ai_family = af;
 
 	/* to determine protocol family, call lookup() first. */
-	err = lookup(m_address.empty() ? "0.0.0.0" : m_address.c_str(), m_port, addr, addrlen);
+	err = lookup(m_address, m_port, addr, addrlen, hints);
 	if (err) {
 		LogError("The local address is invalid - %s", m_address.c_str());
 		return false;
diff --git a/UDPSocket.h b/UDPSocket.h
index ec5de9c..46b2370 100644
--- a/UDPSocket.h
+++ b/UDPSocket.h
@@ -42,6 +42,7 @@ public:
 	~CUDPSocket();
 
 	bool open();
+	bool open(const unsigned int af);
 
 	int  read(unsigned char* buffer, unsigned int length, sockaddr_storage& address, unsigned int &address_length);
 	bool write(const unsigned char* buffer, unsigned int length, const sockaddr_storage& address, unsigned int address_length);
@@ -49,6 +50,9 @@ public:
 	void close();
 
 	static int lookup(const std::string& hostName, unsigned int port, sockaddr_storage &address, unsigned int &address_length);
+	static int lookup(const std::string& hostName, unsigned int port, sockaddr_storage &address, unsigned int &address_length, struct addrinfo &hints);
+	static bool match(const sockaddr_storage &addr1, const sockaddr_storage &addr2);
+	static bool isnone(const sockaddr_storage &addr);
 
 private:
 	std::string    m_address;