ln.snmp/SNMPClient.cs

// /**
//  * File: MyClass.cs
//  * Author: haraldwolff
//  *
//  * This file and it's content is copyrighted by the Author and / or copyright holder.
//  * Any use wihtout proper permission is illegal and may lead to legal actions.
//  *
//  *
//  **/
using System;
using System.Collections.Generic;
using ln.snmp.types;
using System.Net.Sockets;
using System.Net;
using System.Threading;

namespace ln.snmp
{
    public class SNMPClient : IDisposable
    {
        public static bool DEBUG = false;

        public UdpClient LocalEndpoint { get; private set; }
        public int Timeout { get; set; } = 1000;

        private Dictionary<IPEndPoint, InternalRequest> queuedRequests = new Dictionary<IPEndPoint, InternalRequest>();
        private bool shutdown = false;
        private Thread ReceiverThread { get; set; }

        public SNMPClient(IPEndPoint localEndpoint)
        {
            LocalEndpoint = new UdpClient(localEndpoint);
            ReceiverThread = new Thread(Receiver);
            ReceiverThread.Start();
        }

        public void Close()
        {
            shutdown = true;
            LocalEndpoint.Close();
        }

        private void Receiver()
        {
            while (!shutdown)
            {
                try
                {
                    IPEndPoint remoteEndpoint = null;
                    byte[] datagram = LocalEndpoint.Receive(ref remoteEndpoint);

                    lock (queuedRequests)
                    {
                        if (queuedRequests.ContainsKey(remoteEndpoint))
                        {
                            InternalRequest internalRequest = queuedRequests[remoteEndpoint];
                            internalRequest.Response = datagram;
                            lock (internalRequest)
                            {
                                Monitor.PulseAll(internalRequest);
                            }
                        }
                    }


                }
                catch (SocketException se)
                {

                }
                catch (Exception e)
                {
                    Console.WriteLine("Receiver(): {0}", e);
                }
            }
        }

        private byte[] SendRequest(IPEndPoint remoteEndpoint,byte[] request,int timeout)
        {
            InternalRequest internalRequest = new InternalRequest();
            internalRequest.RemoteEndpoint = remoteEndpoint;

            lock(queuedRequests)
            {
                if (queuedRequests.ContainsKey(remoteEndpoint))
                    throw new ArgumentException("Already pending request exists for this remote endpoint", nameof(remoteEndpoint));

                queuedRequests.Add(remoteEndpoint,internalRequest);

                if (DEBUG)
                    Console.WriteLine("SNMPClient: Send:              {0}", BitConverter.ToString(request));

                LocalEndpoint.Send(request, request.Length, remoteEndpoint);

                lock (internalRequest)
                {
                    Monitor.Exit(queuedRequests);
                    bool success = Monitor.Wait(internalRequest, timeout);
                    Monitor.Enter(queuedRequests);
                    if (!success)
                    {
                        throw new TimeoutException();
                    }
                }
                queuedRequests.Remove(remoteEndpoint);
            }

            return internalRequest.Response;
        }


        public Variable SNMPRequest(IPEndPoint remoteEndpoint,Sequence request)
        {
            byte[] response = SendRequest(remoteEndpoint, request.ToBytes(), Timeout);

            if (DEBUG)
                Console.WriteLine("SNMPClient: Received:          {0}", BitConverter.ToString(response));

            Variable vreply = Variable.Read(response);
            return vreply;
        }


        //public abstract List<Variable> Walk(ObjectIdentifier baseOID);
        //public abstract List<Variable> Get(List<ObjectIdentifier> baseOID);

        //public virtual Variable Get(ObjectIdentifier oid)
        //{
        //    return Get(new List<ObjectIdentifier>(new ObjectIdentifier[] { oid }))[0];
        //}

        public void Dispose()
        {
            if (ReceiverThread != null)
            {
                if (ReceiverThread.IsAlive)
                {
                    Close();
                    if (!ReceiverThread.Join(250))
                    {
                        ReceiverThread.Abort();
                    }
                }
                ReceiverThread = null;
            }
        }

        class InternalRequest
        {
            public IPEndPoint RemoteEndpoint;
            public byte[] Response;
        }
    }
}