P2P Messaging

Use the P2P layer to send reliable, typed messages and raw packets between players. Ideal for chat, gameplay events, file chunks, and streaming.

Basics

// Register handlers
client.RegisterMessageHandler<TextMessage>((msg, sender) =>
{
    MelonLogger.Msg($"Message from {sender}: {msg.Content}");
});

// Send to one player
await client.SendTextMessageAsync(targetId, "Hello!");

// Broadcast to everyone
await client.BroadcastTextMessageAsync("Welcome!");

// Pump incoming packets every frame
client.ProcessIncomingMessages();

Sending custom messages

Create a type by inheriting P2PMessage and implement MessageType, Serialize, Deserialize.

using System.Text;

public class CustomMessage : P2PMessage
{
    public override string MessageType => "CUSTOM";
    public string Payload { get; set; } = string.Empty;

    public override byte[] Serialize()
    {
        var json = $"{{{CreateJsonBase(\"\\\"Payload\\\":\\\"{Payload}\\\"\")}}}";
        return Encoding.UTF8.GetBytes(json);
    }

    public override void Deserialize(byte[] data)
    {
        var json = Encoding.UTF8.GetString(data);
        ParseJsonBase(json);
        Payload = ExtractJsonValue(json, "Payload");
    }
}

client.RegisterMessageHandler<CustomMessage>((m, sender) => { /* ... */ });
await client.SendMessageToPlayerAsync(targetId, new CustomMessage { Payload = "Hi" });

File transfer (chunked)

For files, send FileTransferMessage in chunks up to client.P2PManager.MaxPacketSize.

var bytes = File.ReadAllBytes(path);
int chunkSize = client.P2PManager.MaxPacketSize;
int total = (int)Math.Ceiling((double)bytes.Length / chunkSize);

for (int i = 0; i < total; i++)
{
    var slice = bytes.Skip(i * chunkSize).Take(chunkSize).ToArray();

    var file = new FileTransferMessage
    {
        FileName = Path.GetFileName(path),
        FileSize = bytes.Length,
        ChunkIndex = i,
        TotalChunks = total,
        IsFileData = true,
        ChunkData = slice
    };

    await client.SendMessageToPlayerAsync(targetId, file, channel: 1);
}

Channels and reliability

Default channel is 0; you can use multiple channels (e.g., 0 control, 1 files, 2 audio).
Use EP2PSend.k_EP2PSendReliable for reliability; for streams, prefer the message-recommended send type.

Events and sessions