mproxy

Single-threaded NIO TCP proxy (reactor pattern demo, Java 21).

Forwards traffic from a local port to a remote host:port.

Build & run

./mvnw package
java -jar target/mproxy.jar -h <host> -p <port> [-l <local port>] [-v]

Defaults to local port 9999; -v mirrors payloads to stdout.

Design

• One thread, one Selector, zero locks — readiness events drive everything
• Per-connection outbound queues + partial-write handling
• Backpressure via read-pausing between high/low watermarks (128/64 KB)
• Non-blocking upstream connects (OP_CONNECT)
• TCP half-close propagation; per-connection error isolation
• Pooled direct buffers (32 KB)