C# SNMP trap receiver

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C#

.NET

SNMP

I need to trap SNMP and have done the following code, I'm getting the data correctly but the objectID is coming out garbled, is there any reason for this

int port=162;
         UdpClient listener;
        IPEndPoint groupEP;
        byte[] packet = new byte[1024];
        int commlength, miblength, datatype, datalength, datastart, Objecttype, Objectlength;
        int objectstart;
        string objectid;

        string output;

        Console.WriteLine("Initializing SNMP Listener on Port:" + port + "...");

       // try
       // {
            listener = new UdpClient(port);
            groupEP = new IPEndPoint(IPAddress.Any, port);

            while (true)
            {
                Console.WriteLine("Waiting for messages....");
                packet = listener.Receive(ref groupEP);
                Console.WriteLine("Processing new message...");
                if (packet.Length != null)
                {
                Console.Out.WriteLine("New message from {0} :\n {1}\n", groupEP.ToString(), packet);
                if (packet[0] == 0xff)
                {
                    Console.WriteLine("Invalid Packet");
                    return;
                    }

                commlength = Convert.ToInt16(packet[6]);
               miblength = Convert.ToInt16(packet[10 + commlength]);

               Objecttype = Convert.ToInt16(packet[30 + commlength + miblength]);
                Objectlength = Convert.ToInt16(packet[31 + commlength + miblength]);
                objectstart = 32 + commlength + miblength;
                datatype = Convert.ToInt16(packet[26+ Objecttype + Objectlength+commlength+ miblength]);
                datalength = Convert.ToInt16(packet[27 + Objecttype + Objectlength + commlength + miblength]);
                datastart = 28 + Objecttype + Objectlength + commlength + miblength;
                    output = Encoding.ASCII.GetString(packet, datastart, datalength);
                    objectid = Encoding.ASCII.GetString(packet, objectstart , Objectlength);
                Console.WriteLine("sysLocation - Datatype: {0}, Value: {1}", datatype,output);
                Console.WriteLine(objectid);


                }
            }

The data is stored as string hex, would the objectid be stored the same way as it contains '.' I know I can use existing libraries (freely available on the net), but I have just created myself an oppurtunity to learn.

Please advise.