snmp4j初步

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上篇文章我们对SNMP有了一个初步上的认识，这篇文章便准备用开源工具包snmp4j来编程实现一些SNMP的功能。

1.下载
首先到官网下载最新的snmp4j 2.2.5
http://www.snmp4j.org/html/download.html

2.一个比较好的起步点是阅读官方的 javadoc，里面有比较详细的说明和示例代码，可以从org.snmp4j包看起。

一个远程系统是通过创建一个Target实例来被snmp4j识别的。
SNMPv1和SNMPv2c必须使用CommunityTarget，SNMPv3则要使用UserTarget。

一条SNMP消息包括消息的载荷，PDU和消息头。简单来说，消息头用Target表示，而PDU则用以下类来表示：
    PDUv1 (SNMPv1)
    PDU (SNMPv2c)
    ScopedPDU (SNMPv3)

消息发送有2种方式：同步和异步。
异步方式需要实现ResponseListener接口，当消息返回时，这个接口的onResponse(ResponseEvent event)方法会被回调。

3.代码
以下代码演示了同步和异步2种方式获取SNMP消息。
本机是Win7的，自带的SNMP协议是v2版的。(Win7不支持v3)

以下是一些OID的解释
1.3.6.1.2.1.1.1        获取CPU和OS信息
1.3.6.1.2.1.2.1.0      网络接口信息描述
1.3.6.1.2.1.25.6.3.1.2 获取安装的软件信息

import org.snmp4j.CommunityTarget;
import org.snmp4j.PDU;
import org.snmp4j.Snmp;
import org.snmp4j.TransportMapping;
import org.snmp4j.event.ResponseEvent;
import org.snmp4j.event.ResponseListener;
import org.snmp4j.mp.SnmpConstants;
import org.snmp4j.smi.Address;
import org.snmp4j.smi.GenericAddress;
import org.snmp4j.smi.OID;
import org.snmp4j.smi.OctetString;
import org.snmp4j.smi.UdpAddress;
import org.snmp4j.smi.VariableBinding;
import org.snmp4j.transport.DefaultUdpTransportMapping;

public class SnmpTest {

	public static void main(String[] args) throws Exception {
		Address targetAddress = GenericAddress.parse("udp:127.0.0.1/161");
		TransportMapping transport = new DefaultUdpTransportMapping();
		Snmp snmp = new Snmp(transport);
		transport.listen();

		CommunityTarget target = new CommunityTarget();
		target.setCommunity(new OctetString("public"));
		target.setAddress(targetAddress);
		target.setRetries(2);
		target.setTimeout(15000);
		target.setVersion(SnmpConstants.version1);

		PDU pdu = new PDU();
		pdu.add(new VariableBinding(new OID("1.3.6.1.2.1.1.1"))); // sysDescr
		pdu.add(new VariableBinding(new OID("1.3.6.1.2.1.2.1"))); // ifNumber
		pdu.add(new VariableBinding(new OID("1.3.6.1.2.1.25.6.3.1.2"))); // Software
		pdu.setType(PDU.GETNEXT);
		
		//发送同步消息
		ResponseEvent event = snmp.send(pdu, target);

		if (event.getResponse() == null) {
			System.out.println("request timed out");

		} else {
			PDU response = event.getResponse();
			System.out.println("Received synchronous response from: " + event.getPeerAddress());
			// dump response PDU
			System.out.println(response.toString());
			
			//遍历并打印得到的信息
			VariableBinding[] array = response.toArray();
			for (VariableBinding variableBinding : array) {
				System.out.println(variableBinding.getOid() + "=" + variableBinding.getVariable());
				
				//如果是文字，则取得字节数组并打印出人看得懂的中文
				if (variableBinding.getVariable() instanceof OctetString) {
					OctetString octetString = (OctetString)variableBinding.getVariable();
					byte[] value = octetString.getValue();
					String softwareName = new String(value, "GB2312");
					System.out.println(softwareName);
				}
			}
		}
		
		System.out.println();
		
		//发送异步消息
		ResponseListener listener = new ResponseListener() {
		    public void onResponse(ResponseEvent event) {
		       // Always cancel async request when response has been received
		       // otherwise a memory leak is created! Not canceling a request
		       // immediately can be useful when sending a request to a broadcast
		       // address.
		       ((Snmp)event.getSource()).cancel(event.getRequest(), this);
		        PDU response = event.getResponse();
		        PDU request = event.getRequest();
		        if (response == null) {
		            System.out.println("Request "+request+" timed out");
		        }
		        else {
					System.out.println("Received asynchronous response from: " + event.getPeerAddress());
		            System.out.println(response + " on request " + request);
		        }
		    }
		};
		snmp.send(pdu, target, null, listener);
		
		//等待一会儿，不然还没等异步消息接收到，这里程序就直接退出了。
		Thread.sleep(1000);
	}

}

4.运行结果

Received synchronous response from: 127.0.0.1/161
RESPONSE[requestID=1131489612, errorStatus=Success(0), errorIndex=0, VBS[1.3.6.1.2.1.1.1.0 = Hardware: x86 Family 6 Model 42 Stepping 7 AT/AT COMPATIBLE - Software: Windows Version 6.1 (Build 7601 Multiprocessor Free); 1.3.6.1.2.1.2.1.0 = 31; 1.3.6.1.2.1.25.6.3.1.2.1 = 57:69:6e:64:6f:77:73:20:c7:fd:b6:af:b3:cc:d0:f2:b0:fc:20:2d:20:47:6f:6f:67:6c:65:2c:20:49:6e:63:2e:20:28:57:69:6e:55:53:42:29:20:41:6e:64:72:6f:69:64:55:73:62:44:65:76:69:63:65:43:6c:61:73:73]]
1.3.6.1.2.1.1.1.0=Hardware: x86 Family 6 Model 42 Stepping 7 AT/AT COMPATIBLE - Software: Windows Version 6.1 (Build 7601 Multiprocessor Free)
Hardware: x86 Family 6 Model 42 Stepping 7 AT/AT COMPATIBLE - Software: Windows Version 6.1 (Build 7601 Multiprocessor Free)
1.3.6.1.2.1.2.1.0=31
1.3.6.1.2.1.25.6.3.1.2.1=57:69:6e:64:6f:77:73:20:c7:fd:b6:af:b3:cc:d0:f2:b0:fc:20:2d:20:47:6f:6f:67:6c:65:2c:20:49:6e:63:2e:20:28:57:69:6e:55:53:42:29:20:41:6e:64:72:6f:69:64:55:73:62:44:65:76:69:63:65:43:6c:61:73:73
Windows 驱动程序包 - Google, Inc. (WinUSB) AndroidUsbDeviceClass

Received asynchronous response from: 127.0.0.1/161
RESPONSE[requestID=1131489612, errorStatus=Success(0), errorIndex=0, VBS[1.3.6.1.2.1.1.1.0 = Hardware: x86 Family 6 Model 42 Stepping 7 AT/AT COMPATIBLE - Software: Windows Version 6.1 (Build 7601 Multiprocessor Free); 1.3.6.1.2.1.2.1.0 = 31; 1.3.6.1.2.1.25.6.3.1.2.1 = 57:69:6e:64:6f:77:73:20:c7:fd:b6:af:b3:cc:d0:f2:b0:fc:20:2d:20:47:6f:6f:67:6c:65:2c:20:49:6e:63:2e:20:28:57:69:6e:55:53:42:29:20:41:6e:64:72:6f:69:64:55:73:62:44:65:76:69:63:65:43:6c:61:73:73]] on request GETNEXT[requestID=1131489612, errorStatus=Success(0), errorIndex=0, VBS[1.3.6.1.2.1.1.1 = Null; 1.3.6.1.2.1.2.1 = Null; 1.3.6.1.2.1.25.6.3.1.2 = Null]]

5.snmp4j 和 snmp4j-agent
snmp4j可以获取被管节点信息
snmp4j-agent则是写agent端的代理程序的，我们可以自定义一个软件，写一个agent，这样就能被网管软件统一管理了。
另外jdk自带的JMX包也有snmp协议的实现，不过snmp4j可能更方便点。

6.参考资料
使用snmp4j实现Snmp功能 http://blog.csdn.net/clearwater21cn/article/details/2328047 一共3篇