Smack Jingle java.net.BindException: Cannot assign requested address: Cannot bind

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代码  

1. java.net.BindException: Cannot assign requested address: Cannot bind  
2.     at java.net.PlainDatagramSocketImpl.bind0(Native Method)  
3.     at java.net.PlainDatagramSocketImpl.bind(Unknown Source)  
4.     at java.net.DatagramSocket.bind(Unknown Source)  
5.     at java.net.DatagramSocket.<init>(Unknown Source)  
6.     at java.net.DatagramSocket.<init>(Unknown Source)  
7.     at de.javawi.jstun.test.demo.ice.Candidate.<init>(Candidate.java:44)  
8.     at de.javawi.jstun.test.demo.ice.ICENegociator.gatherCandidateAddresses(ICENegociator.java:87)  
9.     at org.jivesoftware.smackx.jingle.nat.ICEResolver.initialize(ICEResolver.java:81)  
10.     at org.jivesoftware.smackx.jingle.nat.TransportResolver.initializeAndWait(TransportResolver.java:387)  
11.     at org.jivesoftware.smackx.jingle.nat.ICETransportManager.<init>(ICETransportManager.java:36)  
12.     at com.haojie.smack.demo.Demo.initialize(Demo.java:84)  
13.     at com.haojie.smack.demo.Demo.<init>(Demo.java:76)  
14.     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代码  

1. java.net.BindException: Cannot assign requested address: Cannot bind  
2.     at java.net.PlainDatagramSocketImpl.bind0(Native Method)  
3.     at java.net.PlainDatagramSocketImpl.bind(Unknown Source)  
4.     at java.net.DatagramSocket.bind(Unknown Source)  
5.     at java.net.DatagramSocket.<init>(Unknown Source)  
6.     at java.net.DatagramSocket.<init>(Unknown Source)  
7.     at de.javawi.jstun.test.demo.ice.Candidate.<init>(Candidate.java:44)  
8.     at de.javawi.jstun.test.demo.ice.ICENegociator.gatherCandidateAddresses(ICENegociator.java:89)  
9.     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: 

Java代码  

1. public Candidate(Address address, short componentId) throws SocketException, UnknownHostException, UtilityException {  
2.     this.socket = new DatagramSocket(0, address.getInetAddress());  
3.     this.type = CandidateType.Local;  
4.     this.componentId = componentId;  
5.     this.priority = 0;  
6.     this.base = this;  
7.     this.isInUse = false;  
8. }  
9.   
10. public Candidate(Address address, CandidateType type, short componentId, Candidate base) throws SocketException, UnknownHostException, UtilityException {  
11.     this.socket = new DatagramSocket(0, address.getInetAddress());  
12.     this.type = type;  
13.     setComponentId(componentId);  
14.     this.priority = 0;  
15.     this.base = base;  
16.     this.isInUse = false;  
17. }  

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: 

Java代码  

1. public class DiscoveryInfo {  
2. .......  
3.     private int publicPort; // 用于保存NAT转换后的端口  
4.     public int getPublicPort() {  
5.         return publicPort;  
6.     }  
7.     public void setPublicPort(int publicPort) {  
8.         this.publicPort = publicPort;  
9.     }  
10. ......  
11. }  
12.   
13. public class ICENegociator {  
14. .......  
15.     public void gatherCandidateAddresses() {  
16.         ......  
17.         DiscoveryTest test = new DiscoveryTest(iaddress, stunServer, stunPort);  
18.         DiscoveryInfo di = test.test();  
19.         if (di.getPublicIP() != null) {  
20.             Candidate cand = new Candidate(new Address(di.getPublicIP().getAddress()), CandidateType.ServerReflexive, componentId, local);  
21.             cand.setPort(di.getPublicPort());  
22.             ......  
23.         }  
24.     }  
25. ......  
26. }  
27.   
28. public class DiscoveryTest {  
29.     private boolean test1() throws UtilityException, SocketException, UnknownHostException, IOException, MessageAttributeParsingException, MessageHeaderParsingException {  
30.         ......  
31.         di.setPublicIP(ma.getAddress().getInetAddress());  
32.         di.setPublicPort(ma.getPort());  
33.         ......  
34.     }  
35. }  
36.   
37. public class Candidate implements Comparable {  
38.     ......  
39.     private int port;  
40.       
41.     public Candidate(Address address, CandidateType type, short componentId, Candidate base) throws SocketException, UnknownHostException, UtilityException {  
42.         if (type == CandidateType.Local) {  
43.             this.socket = new DatagramSocket(0, address.getInetAddress());  
44.             this.address = null;  
45.         } else {  
46.             this.address = address;  
47.             this.socket = null;  
48.         }  
49.           
50.         this.type = type;  
51.         setComponentId(componentId);  
52.         this.priority = 0;  
53.         this.base = base;  
54.         this.isInUse = false;  
55.    }  
56.   
57.    public Address getAddress() throws UtilityException {  
58.        if (type == CandidateType.Local) {  
59.             return new Address(socket.getLocalAddress().getAddress());  
60.         } else {  
61.             return this.address;  
62.         }  
63.     }  
64.       
65.     public int getPort() {  
66.         if (type == CandidateType.Local) {  
67.             return socket.getLocalPort();  
68.         } else {  
69.             return this.port;  
70.         }  
71.     }  
72.       
73.     public void setPort(int port) {  
74.         this.port = port;  
75.     }  
76. }  

 转自：http://mysuperbaby.iteye.com/blog/901370