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

java.net.BindException:Cannotassignrequestedaddress:Cannotbind
atjava.net.PlainDatagramSocketImpl.bind0(NativeMethod)
atjava.net.PlainDatagramSocketImpl.bind(UnknownSource)
atjava.net.DatagramSocket.bind(UnknownSource)
atjava.net.DatagramSocket.<init>(UnknownSource)
atjava.net.DatagramSocket.<init>(UnknownSource)
atde.javawi.jstun.test.demo.ice.Candidate.<init>(Candidate.java:44)
atde.javawi.jstun.test.demo.ice.ICENegociator.gatherCandidateAddresses(ICENegociator.java:87)
atorg.jivesoftware.smackx.jingle.nat.ICEResolver.initialize(ICEResolver.java:81)
atorg.jivesoftware.smackx.jingle.nat.TransportResolver.initializeAndWait(TransportResolver.java:387)
atorg.jivesoftware.smackx.jingle.nat.ICETransportManager.<init>(ICETransportManager.java:36)
atcom.haojie.smack.demo.Demo.initialize(Demo.java:84)
atcom.haojie.smack.demo.Demo.<init>(Demo.java:76)
atcom.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

java.net.BindException:Cannotassignrequestedaddress:Cannotbind
atjava.net.PlainDatagramSocketImpl.bind0(NativeMethod)
atjava.net.PlainDatagramSocketImpl.bind(UnknownSource)
atjava.net.DatagramSocket.bind(UnknownSource)
atjava.net.DatagramSocket.<init>(UnknownSource)
atjava.net.DatagramSocket.<init>(UnknownSource)
atde.javawi.jstun.test.demo.ice.Candidate.<init>(Candidate.java:44)
atde.javawi.jstun.test.demo.ice.ICENegociator.gatherCandidateAddresses(ICENegociator.java:89)
atde.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

publicCandidate(Addressaddress,shortcomponentId)throwsSocketException,UnknownHostException,UtilityException{
this.socket=newDatagramSocket(0,address.getInetAddress());
this.type=CandidateType.Local;
this.componentId=componentId;
this.priority=0;
this.base=this;
this.isInUse=false;
}

publicCandidate(Addressaddress,CandidateTypetype,shortcomponentId,Candidatebase)throwsSocketException,UnknownHostException,UtilityException{
this.socket=newDatagramSocket(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:

Java代码

publicclassDiscoveryInfo{
.......
privateintpublicPort;//用于保存NAT转换后的端口
publicintgetPublicPort(){
returnpublicPort;
}
publicvoidsetPublicPort(intpublicPort){
this.publicPort=publicPort;
}
......
}

publicclassICENegociator{
.......
publicvoidgatherCandidateAddresses(){
......
DiscoveryTesttest=newDiscoveryTest(iaddress,stunServer,stunPort);
DiscoveryInfodi=test.test();
if(di.getPublicIP()!=null){
Candidatecand=newCandidate(newAddress(di.getPublicIP().getAddress()),CandidateType.ServerReflexive,componentId,local);
cand.setPort(di.getPublicPort());
......
}
}
......
}

publicclassDiscoveryTest{
privatebooleantest1()throwsUtilityException,SocketException,UnknownHostException,IOException,MessageAttributeParsingException,MessageHeaderParsingException{
......
di.setPublicIP(ma.getAddress().getInetAddress());
di.setPublicPort(ma.getPort());
......
}
}

publicclassCandidateimplementsComparable{
......
privateintport;

publicCandidate(Addressaddress,CandidateTypetype,shortcomponentId,Candidatebase)throwsSocketException,UnknownHostException,UtilityException{
if(type==CandidateType.Local){
this.socket=newDatagramSocket(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;
}

publicAddressgetAddress()throwsUtilityException{
if(type==CandidateType.Local){
returnnewAddress(socket.getLocalAddress().getAddress());
}else{
returnthis.address;
}
}

publicintgetPort(){
if(type==CandidateType.Local){
returnsocket.getLocalPort();
}else{
returnthis.port;
}
}

publicvoidsetPort(intport){
this.port=port;
}
}

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