i2pplus

Streaming (streaming/)

Implementation of I2P’s streaming protocol, providing TCP-like reliable, ordered, bidirectional connections over I2P’s unreliable garlic messages.

How It Works

The streaming library abstracts I2P’s message-based transport into familiar socket semantics:

1. Connection - Client creates an I2PSocket via I2PSocketManager
2. Handshake - Outbound destination created, connected to peer’s destination
3. Data - Messages fragmented, encrypted, sent through tunnel hops
4. Ack/Nak - Acks confirm delivery, naks trigger retransmission
5. Congestion - Sliding window limits in-flight messages

Retransmission Strategy

Unlike TCP’s cumulative ACKs, I2P uses selective ACKs per-packet:

• Packets have sequence numbers
• Receiver acks individual packets
• Missing acks trigger retransmission after RTO (retransmission timeout)
• Jitter smoothing prevents rapid retransmit floods

Key Classes

Class	Purpose
Connection	Per-stream state (seq, window, RTT)
ConnectionManager	All connections to a destination
PacketHandler	Fragment/reassemble, encrypt/decrypt
MessageHandler	garlic message encoding

Differences from TCP

• No 3-way handshake (destinations pre-established)
• No sliding window (fixed window at sender, acks advance window)
• No FIN (explicit close message)
• Built-in encryption (no TLS needed)

See ministreaming/ for the client API (I2PSocket, I2PServerSocket).

Packages

• net.i2p.client.streaming.impl - Connection, ConnectionManager, PacketHandler, schedulers

Building

# Gradle
./gradlew :apps:streaming:jar

# Ant (from repo root)
ant buildStreaming