How to do a SET using SNMP ?

Question

Hi,
I already ask in the forum Advanced Language Topics
http://forum.java.sun.com/thread.jsp?forum=4&thread=320674
but I din't receive any answer so I try here maybe some one could help me on this ... ;-)
I find a nice piece of code on Internet to do SNMP request �
http://membres.lycos.fr/ysoun/index.html
http://membres.lycos.fr/ysoun/sck.zip
It works find to do some GET operations like doing a GET sysDescr (oid 1.3.6.1.2.1.1.1.0).
But I would like to do a SET operation but I could'nt succeed.
First I do a get on an oid 1.3.6.1.2.1.1.4.0 (sysContact) and I get the value "hello" which is find and I would like to set this value to "good bye".
Well I have to say that I don�t know very well the SNMP protocol and I couldn�t figure out where to put the value in order to set "Good bye". Off course I have the right community to do that but I just can't figure out how can I do that ...
Any comment ... help ... ideas ... are more than welcome !!!! Or maybe some better SNMP package to do that???
thanks,
Emmanuel
Here is the code:
the function to set using SNMP ...
  public static setSnmpRequest(int snmpPort, int snmpTimeout, String community, String host, String strValue){
      String oid = new String("1.3.6.1.2.1.1.4.0");
      D_SNMP.Message request;
      try {
          InetAddress snmpHost = InetAddress.getByName(host);
          DatagramSocket sock = new DatagramSocket();
          sock.setSoTimeout(snmpTimeout);
          // create pdu.
          //somewhere here I should include my variable "good bye" but I don't really know how
          Var var = new Var(oid);
          OctetString c = new OctetString(community);
          D_SNMP.Integer requestId = new D_SNMP.Integer(0);
          D_SNMP.Integer errorIndex = new D_SNMP.Integer(0);
          D_SNMP.Integer errorStatus = new D_SNMP.Integer(0);
          //For the GET:
          //PduCmd pdu = new PduCmd(Pdu.GET,requestId,errorStatus,errorIndex,new VarList(var));
          //What I would like to do:
          PduCmd pdu = new PduCmd(Pdu.SET,requestId,errorStatus,errorIndex,new VarList(var));
          D_SNMP.Message m = new D_SNMP.Message(c,pdu);
          // send
          byte[] b = m.codeBer();
          DatagramPacket packet = new DatagramPacket(b,b.length,snmpHost,snmpPort);
          byte[] b2 = new byte[1024];
          DatagramPacket p2 = new DatagramPacket(b2,b2.length);
          long startTime = System.currentTimeMillis();
          sock.send(packet);
          sock.receive(p2); // block or ... timeout.
          long time = (System.currentTimeMillis() - startTime);
          // display
          ByteArrayInputStream ber = new ByteArrayInputStream(b2,1,p2.getLength()-1); // without tag !
          D_SNMP.Message m2 = new D_SNMP.Message(ber);
          System.out.println("snmpPing " + host + " :");
          System.out.println(m2.getPdu().getVarList().elementAt(0) + " / time = " + time + "ms" );
          if (debug){
              StringBuffer buf = new StringBuffer();
              m2.println("",buf);
              System.out.println(buf);
      } catch (UnknownHostException ex){
          System.out.println(host + ": unknown host." );
      } catch (InterruptedIOException ex){
          System.out.println("snmpPing "+ host + " : Time-out." );
      } catch ( Exception ex) {
          System.out.println("Error in : ");
          System.out.println(ex);
  } the class Var... where somewhere I should be able to set the variable "Good bye" ...
import java.io.*;
import java.util.Vector;
/** ASN.1 grammar for Var:
* Var ::=
* SEQUENCE
*        { name Oid
*          value CHOICE {Null, Integer, Counter, gauge, Timeticks, IpAddress, OctetString}
final public class Var extends construct implements Serializable {
  public Var(Oid o, smi s){
    this();
    valeur.addElement(o);
    valeur.addElement(s);
  /** Same as Var(new Oid(oid), new Null()).
  public Var(String oid) throws IOException{
    this(new Oid(oid), new D_SNMP.Null());
  /** Builds a Var from a ByteArrayInputStream holding a Var Ber coding.
   *  <BR>Bytes read are removed from the stream.
   *  <P><B>Note:</B> The ByteArrayInputStream must not contain the Var Tag.
   *  @exception IOException is thrown if a problem occurs while trying to decode the stream.
  public Var(ByteArrayInputStream inBer) throws IOException{
    this();
    decodeBer(inBer);
  /** Used only by VarList.
  Var(){
    super(smi.SEQUENCE_tag);
    valeur = new Vector(2);
  /** Returns the name of this Var.
  public Oid getName(){
    return (Oid) valeur.elementAt(0);
  /** Returns the value of this Var.
  public smi getValue(){
    return (smi) valeur.elementAt(1);
  /** Returns the value of this Var as a String.
  public String toString() {
    try{
    return ((smi)valeur.elementAt(0)).toString() + " = " + ((smi)valeur.elementAt(1)).toString();
    }catch (IndexOutOfBoundsException e) { // ne doit pas se produire.
      System.out.println("Erreur codage interne type Var.");
      System.exit(1);
    return null;
  /** Used smi.decodeBer().
  void decodeValeur(ByteArrayInputStream bufferBer, int lgBerValeur) throws IOException {
    int tag = bufferBer.read();
    if ( tag != smi.OID_tag )
      throw new IOException ("erreur decodage tag Oid de Var: byte " + java.lang.Integer.toHexString(tag) +" recu.");
    Oid name = new Oid(bufferBer);
    this.valeur.addElement(name);
    // lis l'objet suivant.
    tag = bufferBer.read();
    try{
    smi _valeur = smiFactory.create(tag,bufferBer);
    this.valeur.addElement(_valeur);
    } catch (IOException e){
      throw new IOException ("erreur decodage champ Valeur : " + e);
  /** Custom serialization: Ber coding is written in ObjectOutputStream.
  private void writeObject(ObjectOutputStream out) throws IOException{
    byte b[] = this.codeBer();
    out.writeInt(b.length);
    out.write(b);
    out.flush();
  private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
    this._tag = smi.SEQUENCE_tag;
    this.valeur = new Vector();
    int len = in.readInt();
    byte b[] = new byte[len];
    in.readFully(b);
    this.decodeBer(new ByteArrayInputStream(b,1,b.length-1));
} the class VarList ...
import java.io.*;
import java.util.Vector;
/** ASN.1 grammar for VarList:
* VarList ::=
* SEQUENCE OF Var
final public class VarList extends construct {
  /** Constructs a VarList holding a single Var.
   *  @param Var to be held by Varlist
   public VarList(Var v){
     super(smi.SEQUENCE_tag);
     valeur = new Vector(1);
     valeur.addElement(v);
  /** Constructs a VarList holding Vars.
   *  @param v Vector of Vars.
   public VarList(Vector v){
     super(smi.SEQUENCE_tag);
     valeur = (Vector) v.clone();
   /** Constructs a VarList holding Vars.
   *  @param tab array of Vars.
   public VarList(Var[] tab){
     super(smi.SEQUENCE_tag);
     int taille = tab.length;
     valeur = new Vector(taille);
     for (int i=0; i<taille; i++)
       valeur.addElement(tab);
/** Builds a VarList from a ByteArrayInputStream holding a VarList Ber coding.
* <BR>Bytes read are removed from the stream.
* <P><B>Note:</B> The ByteArrayInputStream must not contain the Var Tag.
* @exception IOException is thrown if a problem occurs while trying to decode the stream.
public VarList(ByteArrayInputStream inBer) throws IOException{
super(smi.SEQUENCE_tag);
valeur = new Vector();
decodeBer(inBer);
/** Returns the Var at the specified index.
public Var elementAt(int i) throws IndexOutOfBoundsException {
return (Var)valeur.elementAt(i); // Sans soucis: Var est immutable
/** Returns the number of Var held this VarList.
public int getSize(){
return valeur.size();
/** Used by smi.decodeBer().
* A VarList is in fact an array of Vars.
void decodeValeur(ByteArrayInputStream bufferBer, int lgBerValeur) throws IOException {
Var v;
int lg;
try{
while (lgBerValeur >0){
int tag = bufferBer.read();
lgBerValeur --;
if ( tag != smi.SEQUENCE_tag )
throw new IOException ("error decoding tag Var in VarList: byte " +
java.lang.Integer.toHexString(tag) +" read.");
v =new Var();
lg = v.decodeBer(bufferBer);
this.valeur.addElement(v);
lgBerValeur -= lg;
} catch (IOException e){
throw new IOException ("error decoding Value : " + e);

Answer 1

I read the documentation it does not help me much, (it's generated by javadoc and there is not enought comment to understand the whole thing ... in fact it just miss a sample of SET request and it would be perfect ...
thanks,
emmanuel
PS: I'm going to try the author again
PS: Still ... any help or pakage to do SET request using SNMP are more than welcome ...