Question

I want to use simple snmp get in android.I found the code for java and try to use it in android.I also attach snmp4j.jar file for android.But I got the NullPointer Exception and I don’t get the output.If anybody have any idea or code for how to use snmp in android then please suggest me..

Following is my code which i have tried,

1   import java.io.IOException;
2   import org.snmp4j.CommunityTarget;
3   import org.snmp4j.PDU;
4   import org.snmp4j.Snmp;
5   import org.snmp4j.TransportMapping;
6   import org.snmp4j.event.ResponseEvent;
7   import org.snmp4j.mp.SnmpConstants; 
8   import org.snmp4j.smi.OID;
9   import org.snmp4j.smi.OctetString;
10  import org.snmp4j.smi.UdpAddress;
11  import org.snmp4j.smi.VariableBinding;
12  import org.snmp4j.transport.DefaultUdpTransportMapping;
13  import android.app.Activity;
14  import android.os.Bundle;
15  import android.util.Log;
16  import android.view.View;
17  import android.view.View.OnClickListener;
18  import android.widget.Button;
19  import android.widget.Toast;
20 
21  public class SNMPClient extends Activity {
22
23  private static String ipAddress = "127.0.0.1";
24  private static String port = "161";
25  //cmd to request from Server
26  private static String oidValue = "1.3.6.1.2.1.1.5.0";
27  private static int snmpVersion = SnmpConstants.version2c;
28  private static String community = "public";
29 
30  public static Snmp snmp;
31  public static CommunityTarget comtarget;
32  static PDU pdu;
33  static OID oid;
34  static VariableBinding req;
35  Button b;
36  private static final String tag = "SNMP CLIENT";
37
38 @Override
39 public void onCreate(Bundle savedInstanceState) {
40    super.onCreate(savedInstanceState);
41    setContentView(R.layout.main);
42    
43    System.setProperty("java.net.preferIPv4Stack", "true");
44      System.setProperty("java.net.preferIPv6Addresses", "false");
45      
46    b = (Button) findViewById(R.id.getvalue);
47    b.setOnClickListener(new OnClickListener() {
48
49        public void onClick(View v) {
50            // TODO Auto-generated method stub
51           try {
52                sendSnmpRequest(oidValue);
53            } catch (IOException e) {
54                // TODO Auto-generated catch block
55                e.printStackTrace();
56            } catch (Exception e) {
57                // TODO Auto-generated catch block
58                e.printStackTrace();
59            }
60
61        }
62    });
63   }
64 
65 private void sendSnmpRequest(String cmd) throws Exception {
66    // Create TransportMapping and Listen
67    TransportMapping transport = new DefaultUdpTransportMapping();
68    transport.listen();
69 
70    // Create Target Address object
71    CommunityTarget comtarget = new CommunityTarget();
72    comtarget.setCommunity(new OctetString(community));
73    comtarget.setVersion(snmpVersion);
74    comtarget.setAddress(new UdpAddress(ipAddress + "/" + port));
75    comtarget.setRetries(2);
76    comtarget.setTimeout(1000);
77    // Prepare PDU
78    req = new VariableBinding();
79    OID oid = new OID(cmd);   
80    req.setOid(oid);
81    pdu = new PDU();
82    pdu.add(req);
83    Snmp snmp = new Snmp(transport);
84    Log.i(tag ,"Sending Request to Agent...");
85    ResponseEvent response = snmp.get(pdu, comtarget);
86    // Process Agent Response
87    if (response != null) {
88        Log.i(tag,"Got Response from Agent");   //upto  this get in Logcat 
89        PDU responsePDU = response.getResponse();  //Here get Null response
90        if (responsePDU != null) {
91            int errorStatus = responsePDU.getErrorStatus();
92            int errorIndex = responsePDU.getErrorIndex();
93            String errorStatusText = responsePDU.getErrorStatusText();
94 
95            if (errorStatus == PDU.noError) {
96                Log.i(tag,"Snmp Get Response = "
97                        + responsePDU.getVariableBindings());
98                Toast.makeText(getApplicationContext(),
99                     "Snmp Get Response = " + responsePDU.getVariableBindings(),Toast.LENGTH_LONG).show();
100            } else {
101                 Log.i((String) tag,"Error: Request Failed");
102                 Log.i(tag,"Error Status = " + errorStatus);
103                 Log.i(tag,"Error Index = " + errorIndex);
104                 Log.i(tag,"Error Status Text = " + errorStatusText);
105             }
106         } else {
107             Log.i(tag,"Error: Response PDU is null");  // This get in Logcat
108         }
109     } else {
110         Log.i(tag,"Error: Agent Timeout... ");
111     }
112     snmp.close();
113 }}

Please anyone have any solution Please suggest me. Thanks in Advance………….

At line 89 get null value so get NUllPointer Exception…….Any idea or code

Answer 1

From the ResponseEvent.getResponse() documentation (emphasis mine):

Returns: a PDU instance if a response has been received. If the
request timed out then null will be returned.

Now obviously you can see that you’re getting the null response at the line:

PDU responsePDU = response.getResponse();

It is most likely because you’re trying to do an SNMP get your Android’s localhost address, i.e.:

private static String ipAddress = "127.0.0.1";
private static String port = "161";
// ...
comtarget.setAddress(new UdpAddress(ipAddress + "/" + port));

This doesn’t make sense because your Android probably does not have the SNMP service running locally, so how you would get a response from an SNMP service that isn’t running?

Try changing that ipAddress to the address of the device you wish to connect to.