如何在JXTA-JXSE 2.6中发现对等体并发送消息？
使用http://jxse.kenai.com/中的 JXTA 2.6我想创建可以在一个或多个主机上运行多个对等的应用程序。 对等体应该能够在组中找到彼此并发送直接消息以及传播消息。
简单的hello world类型的应用程序看起来会满足这些要求吗？
我创建了这个问题的目的是提供一个像答案这样的教程，这个答案在两个月前我很难找到，当我开始查看JXTA的uni项目时。 随意添加自己的答案或改进我的。 我会等几天接受最好的一个。
JXTA 2.6 Peer发现和管道消息传递简介
我希望我2个月前的指南=）
在建立JXTA p2p应用程序的大学课程中花了很多时间之后，我觉得很多挫折和困惑都可以通过良好的起点避免。
您可以在此处找到您需要的jar文件：
https://oss.sonatype.org/content/repositories/comkenaijxse-057/com/kenai/jxse/jxse/2.6/jxse-2.6.jar
http://sourceforge.net/projects/practicaljxta/files/lib-dependencies-2.6.zip/download
将它们扔进Yourproject / lib，打开eclipse，创建一个新项目“Yourproject”，它应该为你排序导出库。
您很快就会意识到，网上几乎所有信息都已过时，非常过时。 您还将遇到许多非常令人困惑的错误消息，并且可以通过检查列表来避免大多数错误消息。
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您的防火墙是否已关闭或至少对您使用的端口打开？ 您可以在Fedora下使用“sudo service iptables stop”禁用iptables。
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检查拼写！ 很多时候，当加入群组或尝试发送拼写群组名称错误的消息时，或者在查找对等点和服务或打开管道时使用完全相同的广告将导致非常混乱的消息。 当我发现群组名称为“Net info”和“Net_info”时，试图弄清楚为什么我的管道连接超时。
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您使用的是JXTA主目录吗？ 您在同一台计算机上运行每个对等一个？
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你真的使用了一个独特的同伴ID吗？ 提供给IDFactory的种子需要足够长，否则你会得到重复。
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关闭SELinux。 我在开发过程中关闭了SELinux，但可以想象它会导致错误。
虽然将所有字段组合在一起是很常见的，但我会介绍它们，以便显示它们所需的位置。
注意：这在2.7中不起作用。 我认为PSE会员有些问题。
public class Hello implements DiscoveryListener, PipeMsgListener { // When developing you should handle these exceptions, I don't to lessen the clutter of start() public static void main(String[] args) throws PeerGroupException, IOException { // JXTA logs a lot, you can configure it setting level here Logger.getLogger("net.jxta").setLevel(Level.ALL); // Randomize a port to use with a number over 1000 (for non root on unix) // JXTA uses TCP for incoming connections which will conflict if more than // one Hello runs at the same time on one computer. int port = 9000 + new Random().nextInt(100); Hello hello = new Hello(port); hello.start(); hello.fetch_advertisements(); } private String peer_name; private PeerID peer_id; private File conf; private NetworkManager manager; public Hello(int port) { // Add a random number to make it easier to identify by name, will also make sure the ID is unique peer_name = "Peer " + new Random().nextInt(1000000); // This is what you will be looking for in Wireshark instead of an IP, hint: filter by "jxta" peer_id = IDFactory.newPeerID(PeerGroupID.defaultNetPeerGroupID, peer_name.getBytes()); // Here the local peer cache will be saved, if you have multiple peers this must be unique conf = new File("." + System.getProperty("file.separator") + peer_name); // Most documentation you will find use a deprecated network manager setup, use this one instead // ADHOC is usually a good starting point, other alternatives include Edge and Rendezvous try { manager = new NetworkManager( NetworkManager.ConfigMode.ADHOC, peer_name, conf.toURI()); } catch (IOException e) { // Will be thrown if you specify an invalid directory in conf e.printStackTrace(); } NetworkConfigurator configurator; try { // Settings Configuration configurator = manager.getConfigurator(); configurator.setTcpPort(port); configurator.setTcpEnabled(true); configurator.setTcpIncoming(true); configurator.setTcpOutgoing(true); configurator.setUseMulticast(true); configurator.setPeerID(peer_id); } catch (IOException e) { // Never caught this one but let me know if you do =) e.printStackTrace(); } } private static final String subgroup_name = "Make sure this is spelled the same everywhere"; private static final String subgroup_desc = "..."; private static final PeerGroupID subgroup_id = IDFactory.newPeerGroupID(PeerGroupID.defaultNetPeerGroupID, subgroup_name.getBytes()); private static final String unicast_name = "This must be spelled the same too"; private static final String multicast_name = "Or else you will get the wrong PipeID"; private static final String service_name = "And dont forget it like i did a million times"; private PeerGroup subgroup; private PipeService pipe_service; private PipeID unicast_id; private PipeID multicast_id; private PipeID service_id; private DiscoveryService discovery; private ModuleSpecAdvertisement mdadv; public void start() throws PeerGroupException, IOException { // Launch the missiles, if you have logging on and see no exceptions // after this is ran, then you probably have at least the jars setup correctly. PeerGroup net_group = manager.startNetwork(); // Connect to our subgroup (all groups are subgroups of Netgroup) // If the group does not exist, it will be automatically created // Note this is suggested deprecated, not sure what the better way is ModuleImplAdvertisement mAdv = null; try { mAdv = net_group.getAllPurposePeerGroupImplAdvertisement(); } catch (Exception ex) { System.err.println(ex.toString()); } subgroup = net_group.newGroup(subgroup_id, mAdv, subgroup_name, subgroup_desc); // A simple check to see if connecting to the group worked if (Module.START_OK != subgroup.startApp(new String[0])) System.err.println("Cannot start child peergroup"); // We will spice things up to a more interesting level by sending unicast and multicast messages // In order to be able to do that we will create to listeners that will listen for // unicast and multicast advertisements respectively. All messages will be handled by Hello in the // pipeMsgEvent method. unicast_id = IDFactory.newPipeID(subgroup.getPeerGroupID(), unicast_name.getBytes()); multicast_id = IDFactory.newPipeID(subgroup.getPeerGroupID(), multicast_name.getBytes()); pipe_service = subgroup.getPipeService(); pipe_service.createInputPipe(get_advertisement(unicast_id, false), this); pipe_service.createInputPipe(get_advertisement(multicast_id, true), this); // In order to for other peers to find this one (and say hello) we will // advertise a Hello Service. discovery = subgroup.getDiscoveryService(); discovery.addDiscoveryListener(this); ModuleClassAdvertisement mcadv = (ModuleClassAdvertisement) AdvertisementFactory.newAdvertisement(ModuleClassAdvertisement.getAdvertisementType()); mcadv.setName("STACK-OVERFLOW:HELLO"); mcadv.setDescription("Tutorial example to use JXTA module advertisement Framework"); ModuleClassID mcID = IDFactory.newModuleClassID(); mcadv.setModuleClassID(mcID); // Let the group know of this service "module" / collection discovery.publish(mcadv); discovery.remotePublish(mcadv); mdadv = (ModuleSpecAdvertisement) AdvertisementFactory.newAdvertisement(ModuleSpecAdvertisement.getAdvertisementType()); mdadv.setName("STACK-OVERFLOW:HELLO"); mdadv.setVersion("Version 1.0"); mdadv.setCreator("sun.com"); mdadv.setModuleSpecID(IDFactory.newModuleSpecID(mcID)); mdadv.setSpecURI("http://www.jxta.org/Ex1"); service_id = IDFactory.newPipeID(subgroup.getPeerGroupID(), service_name.getBytes()); PipeAdvertisement pipeadv = get_advertisement(service_id, false); mdadv.setPipeAdvertisement(pipeadv); // Let the group know of the service discovery.publish(mdadv); discovery.remotePublish(mdadv); // Start listening for discovery events, received by the discoveryEvent method pipe_service.createInputPipe(pipeadv, this); } private static PipeAdvertisement get_advertisement(PipeID id, boolean is_multicast) { PipeAdvertisement adv = (PipeAdvertisement )AdvertisementFactory. newAdvertisement(PipeAdvertisement.getAdvertisementType()); adv.setPipeID(id); if (is_multicast) adv.setType(PipeService.PropagateType); else adv.setType(PipeService.UnicastType); adv.setName("This however"); adv.setDescription("does not really matter"); return adv; } @Override public void discoveryEvent(DiscoveryEvent event) { // Found another peer! Let's say hello shall we! // Reformatting to create a real peer id string String found_peer_id = "urn:jxta:" + event.getSource().toString().substring(7); send_to_peer("Hello", found_peer_id); } private void send_to_peer(String message, String found_peer_id) { // This is where having the same ID is important or else we wont be // able to open a pipe and send messages PipeAdvertisement adv = get_advertisement(unicast_id, false); // Send message to all peers in "ps", just one in our case Set ps = new HashSet (); try { ps.add((PeerID)IDFactory.fromURI(new URI(found_peer_id))); } catch (URISyntaxException e) { // The JXTA peer ids need to be formatted as proper urns e.printStackTrace(); } // A pipe we can use to send messages with OutputPipe sender = null; try { sender = pipe_service.createOutputPipe(adv, ps, 10000); } catch (IOException e) { // Thrown if there was an error opening the connection, check firewall settings e.printStackTrace(); } Message msg = new Message(); MessageElement fromElem = null; MessageElement msgElem = null; try { fromElem = new ByteArrayMessageElement("From", null, peer_id.toString().getBytes("ISO-8859-1"), null); msgElem = new ByteArrayMessageElement("Msg", null, message.getBytes("ISO-8859-1"), null); } catch (UnsupportedEncodingException e) { // Yepp, you want to spell ISO-8859-1 correctly e.printStackTrace(); } msg.addMessageElement(fromElem); msg.addMessageElement(msgElem); try { sender.send(msg); } catch (IOException e) { // Check, firewall, settings. e.printStackTrace(); } } @Override public void pipeMsgEvent(PipeMsgEvent event) { // Someone is sending us a message! try { Message msg = event.getMessage(); byte[] msgBytes = msg.getMessageElement("Msg").getBytes(true); byte[] fromBytes = msg.getMessageElement("From").getBytes(true); String from = new String(fromBytes); String message = new String(msgBytes); System.out.println(message + " says " + from); } catch (Exception e) { // You will notice that JXTA is not very specific with exceptions... e.printStackTrace(); } } /** * We will not find anyone if we are not regularly looking */ private void fetch_advertisements() { new Thread("fetch advertisements thread") { public void run() { while(true) { discovery.getRemoteAdvertisements(null, DiscoveryService.ADV, "Name", "STACK-OVERFLOW:HELLO", 1, null); try { sleep(10000); } catch(InterruptedException e) {} } } }.start(); } }