Support binding specified IP

main.go

@@ -25,6 +25,7 @@ import (
 func main() {
 	var serverAddr = flag.String("s", stun.DefaultServerAddr, "STUN server address")
 	var localPort = flag.Int("p", 0, "The port on which to bind requests, set to 0 to pick a random port")
+	var localIP = flag.String("i", "", "The ip on which to bind requests, set to empty will use default")
 	var behaviorTestMode = flag.Bool("b", false, "Enable NAT behavior test mode")
 	var verboseLevel = flag.Int("v", 0, "Verbose level (0: none, 1: verbose, 2: double verbose, 3: triple verbose)")
 	flag.Parse()
@@ -39,6 +40,7 @@ func main() {
 	client := stun.NewClient()
 	client.SetServerAddr(*serverAddr)
 	client.SetLocalPort(*localPort)
+	client.SetLocalIP(*localIP)
 	client.SetVerbose(*verboseLevel >= 1)
 	client.SetVVerbose(*verboseLevel >= 2)
 

stun/client.go

@@ -25,6 +25,7 @@ import (
 // to discover NAT type.
 type Client struct {
 	serverAddr   string
+	localIP      string
 	localPort    int
 	softwareName string
 	conn         net.PacketConn
@@ -77,6 +78,11 @@ func (c *Client) SetLocalPort(port int) {
 	c.localPort = port
 }
 
+// SetLocalIP allows user to set the local ip address to send request.
+func (c *Client) SetLocalIP(ip string) {
+	c.localIP = ip
+}
+
 // SetSoftwareName allows user to set the name of the software, which is used
 // for logging purpose (NOT used in the current implementation).
 func (c *Client) SetSoftwareName(name string) {
@@ -98,12 +104,18 @@ func (c *Client) Discover() (NATType, *Host, error) {
 	conn := c.conn
 	if conn == nil {
 		var laddr *net.UDPAddr
-		if c.localPort != 0 {
-			laddr, err = net.ResolveUDPAddr("udp", fmt.Sprintf(":%d", c.localPort))
+
+		if c.localPort != 0  || c.localIP != "" {
+			var address = fmt.Sprintf("%s:%d", c.localIP, c.localPort)
+
+			laddr, err = net.ResolveUDPAddr("udp", address)
 			if err != nil {
 				return NATError, nil, err
 			}
+
+			c.logger.Debugln("Local listen address: " + address)
 		}
+
 		conn, err = net.ListenUDP("udp", laddr)
 		if err != nil {
 			return NATError, nil, err
@@ -127,11 +139,15 @@ func (c *Client) BehaviorTest() (*NATBehavior, error) {
 	conn := c.conn
 	if conn == nil {
 		var laddr *net.UDPAddr
-		if c.localPort != 0 {
-			laddr, err = net.ResolveUDPAddr("udp", fmt.Sprintf(":%d", c.localPort))
+		if c.localPort != 0  || c.localIP != "" {
+			var address = fmt.Sprintf("%s:%d", c.localIP, c.localPort)
+
+			laddr, err = net.ResolveUDPAddr("udp", address)
 			if err != nil {
 				return nil, err
 			}
+
+			c.logger.Debugln("Local listen address: " + address)
 		}
 		conn, err = net.ListenUDP("udp", laddr)
 		if err != nil {