Block transfer over DTLS not working for me

[lorenh]

I am having trouble getting block transfer responses to work under DTLS.

I apologize for the length of this code below, but I thought I'd include the whole test so you can see everything I'm doing. The small payload returns perfectly, but the large payload never arrives. What am I doing wrong?

When I disable DTLS, it works fine.

using System;
using System.Text;
using System.Threading;
using Com.AugustCellars.CoAP;
using Com.AugustCellars.CoAP.DTLS;
using Com.AugustCellars.CoAP.Server;
using Com.AugustCellars.CoAP.Server.Resources;
using Com.AugustCellars.COSE;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using PeterO.Cbor;

namespace DtlsReproTest
{
    [TestClass]
    public class UnitTest1
    {
        [TestMethod]
        public void TestMethod1()
        {
            // Set up DTLS pre shared key
            var pskId = "KeyOne";
            var psk = "abcDEFghiJKL";
            var authKey = new OneKey();
            authKey.Add(CoseKeyKeys.KeyType, GeneralValues.KeyType_Octet);
            authKey.Add(CoseKeyKeys.KeyIdentifier, CBORObject.FromObject(Encoding.UTF8.GetBytes(pskId)));
            authKey.Add(CoseKeyParameterKeys.Octet_k, CBORObject.FromObject(Encoding.UTF8.GetBytes(psk)));
            var userKeys = new KeySet();
            userKeys.AddKey(authKey);

            // Create Server
            var server = new CoapServer();
            var endpoint = new DTLSEndPoint(null, userKeys, 5684);
            server.AddEndPoint(endpoint);
            server.Add(new SmallResource("small"));
            server.Add(new LargeResource("large"));
            server.Start();

            Thread.Sleep(500); // let server get spun up

            // Create client DTLS endpoint
            var clientEndpoint = new DTLSClientEndPoint(authKey);
            clientEndpoint.Start();

            // Perform POST to small resource
            var smallRequest = Request.NewPost();
            smallRequest.EndPoint = clientEndpoint;
            smallRequest.URI = new Uri("coaps://localhost/small");
            smallRequest.SetPayload("test payload", MediaType.TextPlain);
            smallRequest.Type = MessageType.CON;
            smallRequest.AckTimeout = -1; // disable retransmission
            smallRequest.Send();

            var smallResponse = smallRequest.WaitForResponse(1000);

            Assert.IsNotNull(smallResponse);  // <==== SUCCEEDS

            // Perform POST to large resource
            var largeRequest = Request.NewPost();
            largeRequest.EndPoint = clientEndpoint;
            largeRequest.URI = new Uri("coaps://localhost/large");
            largeRequest.SetPayload("test payload", MediaType.TextPlain);
            largeRequest.Type = MessageType.CON;
            largeRequest.AckTimeout = -1; // disable retransmission
            largeRequest.Send();

            var largeResponse = largeRequest.WaitForResponse(1000);

            Assert.IsNotNull(largeResponse); // <==== FAILS
        }
    }

    public class SmallResource : Resource
    {
        public SmallResource(string name) : base(name)
        {
        }

        protected override void DoPost(CoapExchange exchange)
        {
            Console.WriteLine("SmallResource received POST");
            exchange.Respond(StatusCode.Content, "small payload");
        }
    }

    public class LargeResource : Resource
    {
        public LargeResource(string name) : base(name)
        {
        }

        protected override void DoPost(CoapExchange exchange)
        {
            Console.WriteLine("LargeResource received POST");
            var largePayload = new StringBuilder()
                .Append("/-------------------------------------------------------------\\\r\n")
                .Append("|                 RESOURCE BLOCK NO. 1 OF 8                   |\r\n")
                .Append("|               [each line contains 64 bytes]                 |\r\n")
                .Append("\\-------------------------------------------------------------/\r\n")
                .Append("/-------------------------------------------------------------\\\r\n")
                .Append("|                 RESOURCE BLOCK NO. 2 OF 8                   |\r\n")
                .Append("|               [each line contains 64 bytes]                 |\r\n")
                .Append("\\-------------------------------------------------------------/\r\n")
                .Append("/-------------------------------------------------------------\\\r\n")
                .Append("|                 RESOURCE BLOCK NO. 3 OF 8                   |\r\n")
                .Append("|               [each line contains 64 bytes]                 |\r\n")
                .Append("\\-------------------------------------------------------------/\r\n")
                .Append("/-------------------------------------------------------------\\\r\n")
                .Append("|                 RESOURCE BLOCK NO. 4 OF 8                   |\r\n")
                .Append("|               [each line contains 64 bytes]                 |\r\n")
                .Append("\\-------------------------------------------------------------/\r\n")
                .Append("/-------------------------------------------------------------\\\r\n")
                .Append("|                 RESOURCE BLOCK NO. 5 OF 8                   |\r\n")
                .Append("|               [each line contains 64 bytes]                 |\r\n")
                .Append("\\-------------------------------------------------------------/\r\n")
                .Append("/-------------------------------------------------------------\\\r\n")
                .Append("|                 RESOURCE BLOCK NO. 6 OF 8                   |\r\n")
                .Append("|               [each line contains 64 bytes]                 |\r\n")
                .Append("\\-------------------------------------------------------------/\r\n")
                .Append("/-------------------------------------------------------------\\\r\n")
                .Append("|                 RESOURCE BLOCK NO. 7 OF 8                   |\r\n")
                .Append("|               [each line contains 64 bytes]                 |\r\n")
                .Append("\\-------------------------------------------------------------/\r\n")
                .Append("/-------------------------------------------------------------\\\r\n")
                .Append("|                 RESOURCE BLOCK NO. 8 OF 8                   |\r\n")
                .Append("|               [each line contains 64 bytes]                 |\r\n")
                .Append("\\-------------------------------------------------------------/\r\n")
                .ToString();

            exchange.Respond(StatusCode.Content, largePayload);
        }
    }
}

[jimsch]

I have duplicated this and have found the error. It was introduced by trying to enforce DTLS sessions.

[lorenh]

Thanks much for looking into it so quickly. After staring at it all day, I'll be looking forward to seeing what it was when you've fixed it.

[lorenh]

Jim, I see you have been working on master and on a NetStandard branch. I'm just wondering what the status of the DTLS block transfer bug is on master currently? Should I be able to pull master and build it locally now and have DTLS block transfer work again, or should I wait a little longer until you get things released?

[jimsch]

I will have a release done by the end of the weekend

[jimsch]

Fixed