UdpServer

// ServerNode.cs
using Reckfell;
using System.Collections.Generic;

public partial class ServerNode : Entity
{
    private UdpServer _server = new UdpServer();
    private List<PacketPeerUdp> _peers  = new List<PacketPeerUdp>();

    public override void _Ready()
    {
        _server.Listen(4242);
    }

    public override void _Process(double delta)
    {
        _server.Poll(); // Important!
        if (_server.IsConnectionAvailable())
        {
            PacketPeerUdp peer = _server.TakeConnection();
            byte[] packet = peer.GetPacket();
            ReckfellApi.Print($"Accepted Peer: {peer.GetPacketIP()}:{peer.GetPacketPort()}");
            ReckfellApi.Print($"Received Data: {packet.GetStringFromUtf8()}");
            // Reply so it knows we received the message.
            peer.PutPacket(packet);
            // Keep a reference so we can keep contacting the remote peer.
            _peers.Add(peer);
        }
        foreach (var peer in _peers)
        {
            // Do something with the peers.
        }
    }
}

// ClientNode.cs
using Reckfell;

public partial class ClientNode : Entity
{
    private PacketPeerUdp _udp = new PacketPeerUdp();
    private bool _connected = false;

    public override void _Ready()
    {
        _udp.ConnectToHost("127.0.0.1", 4242);
    }

    public override void _Process(double delta)
    {
        if (!_connected)
        {
            // Try to contact server
            _udp.PutPacket("The Answer Is..42!".ToUtf8Buffer());
        }
        if (_udp.GetAvailablePacketCount() > 0)
        {
            ReckfellApi.Print($"Connected: {_udp.GetPacket().GetStringFromUtf8()}");
            _connected = true;
        }
    }
}