Smack Jingle库所用的JSTUN库存在的bug

运行Smack Jingle demo时 (http://fisheye.igniterealtime.org/browse/~raw,r=11613/smack/trunk/jingle/extension/source/org/jivesoftware/smackx/jingle/mediaimpl/demo/Demo.java)总会遇到下面的异常:

java.net.BindException: Cannot assign requested address: Cannot bind
	at java.net.PlainDatagramSocketImpl.bind0(Native Method)
	at java.net.PlainDatagramSocketImpl.bind(Unknown Source)
	at java.net.DatagramSocket.bind(Unknown Source)
	at java.net.DatagramSocket.<init>(Unknown Source)
	at java.net.DatagramSocket.<init>(Unknown Source)
	at de.javawi.jstun.test.demo.ice.Candidate.<init>(Candidate.java:44)
	at de.javawi.jstun.test.demo.ice.ICENegociator.gatherCandidateAddresses(ICENegociator.java:87)
	at org.jivesoftware.smackx.jingle.nat.ICEResolver.initialize(ICEResolver.java:81)
	at org.jivesoftware.smackx.jingle.nat.TransportResolver.initializeAndWait(TransportResolver.java:387)
	at org.jivesoftware.smackx.jingle.nat.ICETransportManager.<init>(ICETransportManager.java:36)
	at com.haojie.smack.demo.Demo.initialize(Demo.java:84)
	at com.haojie.smack.demo.Demo.<init>(Demo.java:76)
	at com.haojie.smack.demo.Demo.main(Demo.java:170)

可以发现是所使用的JSTUN库出了问题. JSTUN位于 http://jstun.javawi.de/. 于是下载了jstun-0.7.3.src.tar.gz, 运行其中的de.javawi.jstun.test.demo.ice.ICENegociator, 还是有同样的问题:

java.net.BindException: Cannot assign requested address: Cannot bind
	at java.net.PlainDatagramSocketImpl.bind0(Native Method)
	at java.net.PlainDatagramSocketImpl.bind(Unknown Source)
	at java.net.DatagramSocket.bind(Unknown Source)
	at java.net.DatagramSocket.<init>(Unknown Source)
	at java.net.DatagramSocket.<init>(Unknown Source)
	at de.javawi.jstun.test.demo.ice.Candidate.<init>(Candidate.java:44)
	at de.javawi.jstun.test.demo.ice.ICENegociator.gatherCandidateAddresses(ICENegociator.java:89)
	at de.javawi.jstun.test.demo.ice.ICENegociator.main(ICENegociator.java:176)

经过调试,发现了原因.
ICENegociator类的gatherCandidateAddresses()方法是用来收集candidates地址的, 它首先获取local地址,作为host candidate,然后从这个地址向指定的STUN服务器发送STUN请求,获取server reflexive candidate address. 对于这些地址都会创建一个Candidate对象. 在Candidate类的构造函数里问题出现了, 先看Candidate构造函数:

	public Candidate(Address address, short componentId) throws SocketException, UnknownHostException, UtilityException {
		this.socket = new DatagramSocket(0, address.getInetAddress());
		this.type = CandidateType.Local;
		this.componentId = componentId;
		this.priority = 0;
		this.base = this;
		this.isInUse = false;
	}
	
	public Candidate(Address address, CandidateType type, short componentId, Candidate base) throws SocketException, UnknownHostException, UtilityException {
		this.socket = new DatagramSocket(0, address.getInetAddress());
		this.type = type;
		setComponentId(componentId);
		this.priority = 0;
		this.base = base;
		this.isInUse = false;
	}

在Candidate类的构造函数里,会创建一个DatagramSocket, DatagramSocket构造函数的第二参数是socket要绑定的local address. 对于host candidate, DatagramSocket的创建没有问题,因为host candidate就是local address; 但对于server reflexive candidate address, 问题出现了, 因为这个地址是NAT转换后的地址, socket无法绑定上去的.

所以改动如下, 判断CandidateType, 如果是ServerReflexive, 则不创建socket.主要的代码为:

public class DiscoveryInfo {
.......
    private int publicPort; // 用于保存NAT转换后的端口
    public int getPublicPort() {
        return publicPort;
    }
    public void setPublicPort(int publicPort) {
        this.publicPort = publicPort;
    }
......
}

public class ICENegociator {
.......
    public void gatherCandidateAddresses() {
        ......
        DiscoveryTest test = new DiscoveryTest(iaddress, stunServer, stunPort);
        DiscoveryInfo di = test.test();
        if (di.getPublicIP() != null) {
            Candidate cand = new Candidate(new Address(di.getPublicIP().getAddress()), CandidateType.ServerReflexive, componentId, local);
            cand.setPort(di.getPublicPort());
            ......
        }
    }
......
}

public class DiscoveryTest {
    private boolean test1() throws UtilityException, SocketException, UnknownHostException, IOException, MessageAttributeParsingException, MessageHeaderParsingException {
        ......
        di.setPublicIP(ma.getAddress().getInetAddress());
        di.setPublicPort(ma.getPort());
        ......
    }
}

public class Candidate implements Comparable {
    ......
    private int port;
    
    public Candidate(Address address, CandidateType type, short componentId, Candidate base) throws SocketException, UnknownHostException, UtilityException {
        if (type == CandidateType.Local) {
        	this.socket = new DatagramSocket(0, address.getInetAddress());
        	this.address = null;
        } else {
        	this.address = address;
        	this.socket = null;
        }
        
        this.type = type;
        setComponentId(componentId);
        this.priority = 0;
        this.base = base;
        this.isInUse = false;
   }

   public Address getAddress() throws UtilityException {
       if (type == CandidateType.Local) {
            return new Address(socket.getLocalAddress().getAddress());
    	} else {
            return this.address;
    	}
    }
    
    public int getPort() {
    	if (type == CandidateType.Local) {
    		return socket.getLocalPort();
    	} else {
    		return this.port;
    	}
    }
    
    public void setPort(int port) {
    	this.port = port;
    }
}