Duplex Pipes

NexNet has a limitation where the total serialized argument size cannot exceed 65,535 bytes. For larger data transfers, NexNet provides built-in duplex pipe support via the INexusDuplexPipe argument, allowing bidirectional byte streaming between server and client.

When to Use Duplex Pipes

Use duplex pipes when you need to:

Transfer data larger than the 65,535 byte argument limit
Stream data continuously (e.g., file transfers)
Send and receive byte data simultaneously

For streaming typed data (classes, structs), consider using Channels instead, which build on top of duplex pipes with type safety.

Defining a Pipe Method

Add an INexusDuplexPipe parameter to a nexus interface method:

public interface IServerNexus
{
    ValueTask UploadFile(string fileName, INexusDuplexPipe pipe);
}

Methods with INexusDuplexPipe must return ValueTask. They cannot return void or ValueTask<T>, and cannot use CancellationToken (pipes have built-in cancellation/completion notifications).

Reading and Writing

The INexusDuplexPipe provides Input and Output properties based on System.IO.Pipelines:

[Nexus<IServerNexus, IClientNexus>(NexusType = NexusType.Server)]
partial class ServerNexus
{
    public async ValueTask UploadFile(string fileName, INexusDuplexPipe pipe)
    {
        while (true)
        {
            var result = await pipe.Input.ReadAsync();
            var buffer = result.Buffer;

            // Process the received bytes
            foreach (var segment in buffer)
            {
                // Write to file, etc.
            }

            pipe.Input.AdvanceTo(buffer.End);

            if (result.IsCompleted)
                break;
        }
    }
}

Thread Safety

As with System.IO.Pipelines, the INexusDuplexPipe is not thread safe. You are responsible for ensuring that member calls do not overlap. Do not read and write from multiple threads simultaneously without synchronization.

Congestion Control

NexNet duplex pipes include built-in congestion control. When the receiving side cannot process data fast enough, backpressure is applied to the sender automatically through the pipeline flow control mechanism.