Write past end of buffer error when sending byte[] using SendNamedMessage

Description

This bug is about Custom Messages. When trying to send a byte[] Using SendNamedMessage you get a “Write past end of buffer error”

Reproduce Steps

1. Write a script that sends a simple byte[] to a client.
2. The FastBufferArray will write perfectly fine, but The SendNamedMessage will get an “Write past end of buffer error”;

Actual Outcome

SendNamedMessage with a byte[] will give an error

Expected Outcome

The written FastBufferArray will be send without issue

My code:

public void SendChunkMessage(byte[] messageContent, ulong clientID)
    {
        int writeSize = FastBufferWriter.GetWriteSize(messageContent);
        FastBufferWriter writer = new FastBufferWriter(writeSize, Allocator.Temp);
        CustomMessagingManager customMessagingManager = NetworkManager.CustomMessagingManager;
        using (writer)
        {
            writer.TryBeginWrite(writeSize);
            writer.WriteBytes(messageContent, writeSize, 0);
            Debug.Log("Written to FastBufferWriter");
            if (IsServer)
            {
                customMessagingManager.SendNamedMessage("Chunk", clientID, writer);
            }
        }
        Debug.Log("Send to client");
    }

My error:

Environment

• OS: Windows 10 pro
• Unity Version: 2022.2.0b16
• Netcode Version: 1.1.0

[ShadauxCat]

Very belated response… Sorry about that.

The default value of -1 is not actually intended to be an “infinite growth” value. Note the documentation:

Maximum size the buffer can grow to. If less than size, buffer cannot grow.

The default of -1 is always going to be less than the size. Constructing without a third argument isn’t intended to create an infinite-growth buffer - the default behavior is a non-growing buffer that won’t exceed the size you give it.

[TheCaveOfWonders]

(at least I believe that is what the issue is…or it is a bug and the default -1 doesn’t automatically adjust)

@NoelStephensUnity I believe the default -1 is bugged and doesn’t automatically adjust the size.

It does adjust the size (this is pretty thoroughly tested both by unit tests and by usage throughout the SDK) but only up to a set maximum. If you’re sending with Unreliable delivery, the max is 1300 bytes, because unreliable delivery, at the transport and even kernel level, has to fit into a single UDP datagram. FastBufferWriter won’t expand beyond that size because the delivery method won’t allow it - if it did, what would happen is that instead of the error you’re seeing, you’d see a more confusing error later on, or possibly your message would be silently lost as the network wouldn’t be able to deliver it.

As Noel said, if you switch to ReliableFragmentedSequenced, this should allow the buffer to grow large enough to fit your data.

Oh sorry my comment was unrelated to this actual issue, it was specifically about the default -1 value. Just tested it in my project when I saw Noel’s message, I tried it again now just to see (in case it was bugged before cause it had never worked for me).

This works fine (the size of values is 16)

  using (FastBufferWriter writer = new FastBufferWriter(8, Allocator.Temp, 256))
                {
                    writer.WriteValueSafe(values);
                    NetworkManager.Singleton.CustomMessagingManager.SendNamedMessage(SharedConstants.Network.Tech.SyncTech, senderClientId, writer);
                }

This won’t work and will throw a “Write past end of buffer” exception. (the size of values is 16)

  using (FastBufferWriter writer = new FastBufferWriter(8, Allocator.Temp))
                {
                    writer.WriteValueSafe(values);
                    NetworkManager.Singleton.CustomMessagingManager.SendNamedMessage(SharedConstants.Network.Tech.SyncTech, senderClientId, writer);
                }