我要评论引言
snmp（简单网络管理协议）是一种用于网络设备管理的标准协议。本文将介绍如何使用 java 和 snmp4j（一个开源的 snmp 实现库）进行 snmp 操作。我们将通过编写 snmputil 类来演示如何进行 snmp 初始化、创建 pdu、发送 snmp 请求并处理响应。
环境准备
首先，确保您已经添加了 snmp4j 依赖。可以通过 maven 或 gradle 进行依赖管理。
<dependency>
<groupid>org.snmp4j</groupid>
<artifactid>snmp4j</artifactid>
<version>2.8.6</version>
</dependency>implementation 'org.snmp4j:snmp4j:2.8.6'
snmputil 类概述
以下是编写 snmputil 类的整体结构。该类提供了静态方法来初始化 snmp、创建 snmp 目标、创建 pdu、发送 snmp 请求和处理响应。
类的静态初始化
我们在这使用静态块来初始化 snmp 对象，确保整个应用程序生命周期中只进行一次初始化。
public class snmputil {
private static final logger log = loggerfactory.getlogger(snmputil.class);
private static snmp snmp = null;
static {
try {
initsnmp();
} catch (ioexception e) {
log.error("snmp 初始化失败", e);
}
}
private static synchronized void initsnmp() throws ioexception {
if (snmp == null) {
messagedispatcher messagedispatcher = new messagedispatcherimpl();
messagedispatcher.addmessageprocessingmodel(new mpv1());
messagedispatcher.addmessageprocessingmodel(new mpv2c());
octetstring localengineid = new octetstring(mpv3.createlocalengineid());
usm usm = new usm(securityprotocols.getinstance().adddefaultprotocols(), localengineid, 0);
usmuser user = new usmuser(new octetstring("snmpv3"), authsha.id, new octetstring("authpassword"),
privaes128.id, new octetstring("privpassword"));
usm.adduser(user.getsecurityname(), user);
messagedispatcher.addmessageprocessingmodel(new mpv3(usm));
transportmapping<?> transportmapping = new defaultudptransportmapping();
snmp = new snmp(messagedispatcher, transportmapping);
snmp.listen();
}
}
}
创建目标
编写createtarget 方法用于创建 snmp 目标，支持 snmp v1, v2c 和 v3 版本。
private static target createtarget(int version, string community, string ipaddress, int port) {
target target = null;
if (!(version == snmpconstants.version3 || version == snmpconstants.version2c || version == snmpconstants.version1)) {
log.error("参数version异常");
return target;
}
if (version == snmpconstants.version3) {
target = new usertarget();
target.setsecuritylevel(securitylevel.auth_priv);
target.setsecurityname(new octetstring("snmpv3"));
} else {
target = new communitytarget();
((communitytarget) target).setcommunity(new octetstring(community));
if (version == snmpconstants.version2c) {
target.setsecuritymodel(securitymodel.security_model_snmpv2c);
}
}
target.setversion(version);
target.setaddress(genericaddress.parse("udp:" + ipaddress + "/" + port));
target.setretries(5);
target.settimeout(3000);
return target;
}创建 pdu
编写createpdu 方法用于创建 protocol data unit (pdu)，这是 snmp 消息的基本构成单元。
private static pdu createpdu(int version, int type, string oid) {
pdu pdu = null;
if (version == snmpconstants.version3) {
pdu = new scopedpdu();
} else {
pdu = new pduv1();
}
pdu.settype(type);
pdu.add(new variablebinding(new oid(oid)));
return pdu;
}
private static pdu createpdu(int version, int type, list<string> oids) {
pdu pdu = null;
if (version == snmpconstants.version3) {
pdu = new scopedpdu();
} else {
pdu = new pdu();
}
pdu.settype(type);
for (string oid : oids) {
pdu.add(new variablebinding(new oid(oid)));
}
return pdu;
}发送 snmp 请求
编写snmpwalk 方法用于发送 getnext 请求，并处理响应。此处注意，不一定都是用getnext请求，也可以用get请求，两者区别故名思义，一个是获取下一条oid，一个是获取自己本身
public static pdu snmpwalk(string ipaddr, int port, int version, string community, string oid) {
try {
target target = createtarget(version, community, ipaddr, port);
pdu pdu = createpdu(version, pdu.getnext, oid);
responseevent responseevent = snmp.send(pdu, target);
pdu response = responseevent.getresponse();
return response;
} catch (ioexception e) {
log.error("snmp 发送请求失败", e);
return new pdu();
}
}
public static pdu snmpwalk(string ipaddr, int port, int version, string community, list<string> oids) {
try {
target target = createtarget(version, community, ipaddr, port);
pdu pdu = createpdu(version, pdu.getnext, oids);
responseevent responseevent = snmp.send(pdu, target);
pdu response = responseevent.getresponse();
return response;
} catch (ioexception e) {
log.error("snmp 发送请求失败", e);
return new pdu();
}
}处理 snmp 响应
编写snmpwalkall 和 snmpwalksegment 方法用于处理连续的 snmp 响应，直到到达 mib 的末尾。
public static list<variablebinding> snmpwalkall(string ipaddr, int port, int version, string community, string startoid) {
list<variablebinding> results = new arraylist<>();
target target = createtarget(version, community, ipaddr, port);
pdu pdu = new pdu();
pdu.add(new variablebinding(new oid(startoid)));
while (true) {
try {
pdu.settype(pdu.getnext);
responseevent responseevent = snmp.send(pdu, target);
pdu response = responseevent.getresponse();
if (response != null && response.size() > 0 && response.geterrorstatus() == 0) {
if (response.get(0).getvariable().tostring().equals("endofmibview")) {
break;
}
results.addall(response.getvariablebindings());
pdu.setrequestid(null); // reset request id for the next request
pdu.remove(0); // remove the old request
pdu.add(response.get(0)); // add the new request based on the last response
} else {
break;
}
} catch (ioexception e) {
log.error("snmp 发送请求失败", e);
break;
}
}
return results;
}
// ...其他代码见完整代码
完整代码
import org.slf4j.logger;
import org.slf4j.loggerfactory;
import org.snmp4j.*;
import org.snmp4j.event.responseevent;
import org.snmp4j.mp.mpv1;
import org.snmp4j.mp.mpv2c;
import org.snmp4j.mp.mpv3;
import org.snmp4j.mp.snmpconstants;
import org.snmp4j.security.*;
import org.snmp4j.smi.genericaddress;
import org.snmp4j.smi.oid;
import org.snmp4j.smi.octetstring;
import org.snmp4j.smi.variablebinding;
import org.snmp4j.transport.defaultudptransportmapping;
import java.io.ioexception;
import java.util.arraylist;
import java.util.list;
public class snmputil {
private static final logger log = loggerfactory.getlogger(snmputil.class);
private static snmp snmp = null; // 将共享资源的访问控制为静态初始化
static {
// 将 snmp 对象的初始化放在静态块中，确保只初始化一次
try {
initsnmp();
} catch (ioexception e) {
log.error("snmp 初始化失败", e); // 记录初始化失败的异常信息
}
}
private static synchronized void initsnmp() throws ioexception { // 添加 synchronized 关键字保证线程安全
if (snmp == null) {
messagedispatcher messagedispatcher = new messagedispatcherimpl();
messagedispatcher.addmessageprocessingmodel(new mpv1());
messagedispatcher.addmessageprocessingmodel(new mpv2c());
octetstring localengineid = new octetstring(mpv3.createlocalengineid());
usm usm = new usm(securityprotocols.getinstance().adddefaultprotocols(), localengineid, 0);
usmuser user = new usmuser(new octetstring("snmpv3"), authsha.id, new octetstring("authpassword"),
privaes128.id, new octetstring("privpassword"));
usm.adduser(user.getsecurityname(), user);
messagedispatcher.addmessageprocessingmodel(new mpv3(usm));
transportmapping<?> transportmapping = new defaultudptransportmapping();
snmp = new snmp(messagedispatcher, transportmapping);
snmp.listen();
}
}
private static target createtarget(int version, string community, string ipaddress, int port) {
target target = null;
if (!(version == snmpconstants.version3 || version == snmpconstants.version2c || version == snmpconstants.version1)) {
log.error("参数version异常"); // 保持错误日志记录
return target;
}
if (version == snmpconstants.version3) {
target = new usertarget();
target.setsecuritylevel(securitylevel.auth_priv);
target.setsecurityname(new octetstring("snmpv3"));
} else {
target = new communitytarget();
((communitytarget) target).setcommunity(new octetstring(community));
if (version == snmpconstants.version2c) {
target.setsecuritymodel(securitymodel.security_model_snmpv2c);
}
}
target.setversion(version);
target.setaddress(genericaddress.parse("udp:" + ipaddress + "/" + port));
target.setretries(5);
target.settimeout(3000);
return target;
}
/**
* 创建 pdu 对象
* @param version
* @param type
* @param oid
* @return
*/
private static pdu createpdu(int version, int type, string oid) {
pdu pdu = null;
if (version == snmpconstants.version3) {
pdu = new scopedpdu();
} else {
pdu = new pduv1();
}
pdu.settype(type);
pdu.add(new variablebinding(new oid(oid)));
return pdu;
}
/**
* 创建 pdu 对象
* @param version
* @param type
* @param oids
* @return
*/
private static pdu createpdu(int version, int type, list<string> oids) {
pdu pdu = null;
if (version == snmpconstants.version3) {
pdu = new scopedpdu();
} else {
pdu = new pdu();
}
pdu.settype(type);
for (string oid : oids) {
pdu.add(new variablebinding(new oid(oid)));
}
return pdu;
}
/**
* 获取 snmp 响应
* @param ipaddr
* @param port
* @param version
* @param community
* @param oid
* @return
*/
public static pdu snmpwalk(string ipaddr, int port, int version, string community, string oid) {
try {
// 由于 snmp 对象已在静态块中初始化，这里不再需要调用 initsnmp
target target = createtarget(version, community, ipaddr, port);
pdu pdu = createpdu(version, pdu.getnext, oid); // 保持内部字符串不变
responseevent responseevent = snmp.send(pdu, target);
pdu response = responseevent.getresponse();
return response;
} catch (ioexception e) {
log.error("snmp 发送请求失败", e); // 增加异常日志记录
return new pdu(); // 在异常情况下仍然返回一个新的 pdu 对象，但已记录错误信息
}
}
/**
* 获取 snmp 响应
* @param ipaddr
* @param port
* @param version
* @param community
* @param oids
* @return
*/
public static pdu snmpwalk(string ipaddr, int port, int version, string community, list<string> oids) {
try {
// 由于 snmp 对象已在静态块中初始化，这里不再需要调用 initsnmp
target target = createtarget(version, community, ipaddr, port);
pdu pdu = createpdu(version, pdu.getnext, oids); // 保持内部字符串不变
responseevent responseevent = snmp.send(pdu, target);
pdu response = responseevent.getresponse();
return response;
} catch (ioexception e) {
log.error("snmp 发送请求失败", e); // 增加异常日志记录
return new pdu(); // 在异常情况下仍然返回一个新的 pdu 对象，但已记录错误信息
}
}
/**
* 获取 snmp 响应
* @param ipaddr
* @param port
* @param version
* @param community
* @param startoid
* @return
*/
public static list<variablebinding> snmpwalkall(string ipaddr, int port, int version, string community, string startoid) {
list<variablebinding> results = new arraylist<>();
target target = createtarget(version, community, ipaddr, port);
pdu pdu = new pdu();
pdu.add(new variablebinding(new oid(startoid)));
while (true) {
try {
pdu.settype(pdu.getnext);
responseevent responseevent = snmp.send(pdu, target);
pdu response = responseevent.getresponse();
if (response != null && response.size() > 0 && response.geterrorstatus() == 0) {
if (response.get(0).getvariable().tostring().equals("endofmibview")) {
break;
}
results.addall(response.getvariablebindings());
pdu.setrequestid(null); // reset request id for the next request
pdu.remove(0); // remove the old request
pdu.add(response.get(0)); // add the new request based on the last response
} else {
break;
}
} catch (ioexception e) {
log.error("snmp 发送请求失败", e);
break;
}
}
return results;
}
/**
* 获取 snmp 响应
* @param ipaddr
* @param port
* @param version
* @param community
* @param startoid
* @return
*/
public static list<variablebinding> snmpwalksegment(string ipaddr, int port, int version, string community, string startoid) {
list<variablebinding> results = new arraylist<>();
target target = createtarget(version, community, ipaddr, port);
pdu pdu = new pdu();
pdu.add(new variablebinding(new oid(startoid)));
while (true) {
try {
pdu.settype(pdu.getnext);
responseevent responseevent = snmp.send(pdu, target);
pdu response = responseevent.getresponse();
if (response != null && response.size() > 0 && response.geterrorstatus() == 0) {
variablebinding vb = response.get(0);
results.add(vb);
// check if we have reached the end of the branch
if (!vb.getoid().startswith(new oid(startoid)) || vb.getvariable().tostring().equals("endofmibview")) {
break;
}
pdu.setrequestid(null); // reset request id for the next request
pdu.remove(0); // remove the old request
pdu.add(vb); // add the new request based on the last response
system.out.println("oid: " + vb.getoid() + ", value: " + vb.getvariable());
} else {
break;
}
} catch (ioexception e) {
log.error("snmp 发送请求失败", e);
break;
}
}
return results;
}
public static list<variablebinding> snmpwalksegment(string ipaddr, int port, int version, string community, list<string> startoids) {
list<variablebinding> results = new arraylist<>();
target target = createtarget(version, community, ipaddr, port);
for(string startoid: startoids){
pdu pdu = new pdu();
pdu.add(new variablebinding(new oid(startoid)));
while (true) {
try {
pdu.settype(pdu.getnext);
responseevent responseevent = snmp.send(pdu, target);
pdu response = responseevent.getresponse();
if (response != null && response.size() > 0 && response.geterrorstatus() == 0) {
variablebinding vb = response.get(0);
results.add(vb);
// check if we have reached the end of the branch
if (!vb.getoid().startswith(new oid(startoid)) || vb.getvariable().tostring().equals("endofmibview")) {
break;
}
pdu.setrequestid(null); // reset request id for the next request
pdu.remove(0); // remove the old request
pdu.add(vb); // add the new request based on the last response
system.out.println("oid: " + vb.getoid() + ", value: " + vb.getvariable());
} else {
break;
}
} catch (ioexception e) {
log.error("snmp 发送请求失败", e);
break;
}
}
}
return results;
}
public static void main(string[] args) {
pdu response = snmputil.snmpwalk("127.0.0.1", 161, snmpconstants.version2c, "public", ".1");
if (response != null && response.geterrorstatus() == 0) {
for (variablebinding vb : response.getvariablebindings()) {
system.out.println("oid: " + vb.getoid() + ", value: " + vb.getvariable());
}
} else {
system.out.println("error in response: " + response.geterrorstatustext());
}
}
}
总结
通过本文的讲解，您应该已经掌握了如何使用 java 和 snmp4j 库进行 snmp 操作。我们介绍了 snmputil 类的设计和实现，包括 snmp 初始化、创建目标、创建 pdu、发送 snmp 请求和处理响应等内容。希望这篇教程能够帮助您更好地理解和使用 snmp4j 进行网络设备管理
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