SNMP4J服务端连接超时问题解决方案

时间:2021-07-13 16:18:34

我们的网络管理中心作为管理中心,是服务端!各个被管设备通过交换机作为客户端与网管中心进行通信,使用的TCP/IP协议!

SNMP只是一种协议包,SNMP4J作为SNMP使用的Java工具包,提供了方便安全的工具包功能!

但是在使用中发现一个问题就是,服务端与客户端发送消息时,发送数次后就不再发送数据了!网络抓包也抓不到,跟踪断点到SNMP4J的代码中发现了这样一个问题!

?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
/**
 * Sends a SNMP message to the supplied address.
 *
 * @param address
 *      an <code>TcpAddress</code>. A
 *      <code>ClassCastException</code> is thrown if
 *      <code>address</code> is not a <code>TcpAddress</code>
 *      instance.
 * @param message
 *      byte[] the message to sent.
 * @throws IOException
 */
public void sendMessage(Address address, byte[] message)
        throws java.io.IOException {
    if (server == null) {
        listen();
    }
    serverThread.sendMessage(address, message);
}

我们可以看到,他与UDP的不同是,使用了一个服务的线程!

?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
public void sendMessage(Address address, byte[] message)
        throws java.io.IOException {
    Socket s = null;
    SocketEntry entry = (SocketEntry) sockets.get(address);
    if (logger.isDebugEnabled()) {
        logger.debug("Looking up connection for destination '"
                + address + "' returned: " + entry);
        logger.debug(sockets.toString());
    }
    if (entry != null) {
        s = entry.getSocket();
    }
    if ((s == null) || (s.isClosed()) || (!s.isConnected())) {
        if (logger.isDebugEnabled()) {
            logger.debug("Socket for address '" + address
                    + "' is closed, opening it...");
        }
        pending.remove(entry);
        SocketChannel sc = null;
        try {
            // Open the channel, set it to non-blocking, initiate
            // connect
            sc = SocketChannel.open();
            sc.configureBlocking(false);
            sc
                    .connect(new InetSocketAddress(
                            ((TcpAddress) address).getInetAddress(),
                            ((TcpAddress) address).getPort()));
            s = sc.socket();
            entry = new SocketEntry((TcpAddress) address, s);
            entry.addMessage(message);
            sockets.put(address, entry);
 
            synchronized (pending) {
                pending.add(entry);
            }
 
            selector.wakeup();
            logger.debug("Trying to connect to " + address);
        } catch (IOException iox) {
            logger.error(iox);
            throw iox;
        }
    } else {
        entry.addMessage(message);
        synchronized (pending) {
            pending.add(entry);
        }
        selector.wakeup();
    }
}

他从一个Map中去获得连接 SocketEntry ,然后得到连接对象Socket!

判断Socket是否有效,有效则直接发送,无效则创建连接后再发送!

然后我找到这样一段代码

?
1
2
3
4
5
private synchronized void timeoutSocket(SocketEntry entry) {
  if (connectionTimeout > 0) {
    socketCleaner.schedule(new SocketTimeout(entry), connectionTimeout);
  }
}

也就是说服务端会自己检查的连接并且去清除他!

我尝试设置 connectionTimeout 的值

?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
private void init() throws UnknownHostException, IOException {
  threadPool = ThreadPool.create("Trap", 2);
  dispatcher = new MultiThreadedMessageDispatcher(threadPool,new MessageDispatcherImpl());
  // 本地IP与监听端口
  listenAddress = GenericAddress.parse(System.getProperty("snmp4j.listenAddress", "tcp:192.168.9.69/5055"));
  DefaultTcpTransportMapping transport;
  transport = new DefaultTcpTransportMapping((TcpAddress) listenAddress);
  transport.setConnectionTimeout(0);
  snmp = new Snmp(dispatcher, transport);
  snmp.getMessageDispatcher().addMessageProcessingModel(new MPv1());
  snmp.getMessageDispatcher().addMessageProcessingModel(new MPv2c());
  snmp.getMessageDispatcher().addMessageProcessingModel(new MPv3());
  USM usm = new USM(SecurityProtocols.getInstance(), new OctetString(MPv3.createLocalEngineID()), 0);
  SecurityModels.getInstance().addSecurityModel(usm);
  snmp.listen();
}

增加一行代码 设置DefaultTcpTransportMapping的超时时间是 0 !

然后就没有问题了!

虽然临时解决了问题,但是由于对SNMP4J不够深入了解,我怕问题恐怕不是这样的!

我在此也希望使用SNMP4J为工具,且作为服务端,在发送数据时有问题的解决方法!

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持服务器之家。

原文链接:https://www.iteye.com/blog/cuisuqiang-1685183