This subtree is intentionally standalone. The Go code stays in place as the behavior reference, while the C implementation builds its own binaries under c/bin/.

Build

make -j$(nproc)

Build outputs:

./bin/udpserver
./bin/udppeer
./bin/udpping
./bin/udprelay
./bin/kcpserver
./bin/kcppeer
./bin/kcpping

Python extension build:

make python-ext
make python-install

Run On Different Machines

Server D runs the KCP hub on 0.0.0.0:10909:

./bin/kcpserver -listen 0.0.0.0:10909 \
  -telemetry-peer peer-a-telemetry \
  -telemetry-interval 1000ms \
  -kcp-session-stats-log logs/d-kcp-stats.jsonl \
  -kcp-session-stats-interval 1000ms

For multi-hour runs, keep -latency-log and -kcp-ts-debug-log off unless you are collecting a short repro trace.

Relay C runs a raw UDP forwarder to D:

./bin/kcpserver -mode=relay -listen 0.0.0.0:10909 -relay-remote 172.21.32.15:10909

Peer A dials D through relay C:

./bin/kcppeer -id peer-a -server 172.21.32.15:10909 -relay-via 106.55.173.235:10909 \
  -inbox-dir inbox/a \
  -latency-log logs/a-latency.jsonl \
  -kcp-ts-debug-log logs/a-kcp-ts.jsonl \
  -kcp-session-stats-log logs/a-kcp-stats.jsonl

Peer B dials D directly:

./bin/kcppeer -id peer-b -server 81.70.156.140:10909 \
  -inbox-dir inbox/b \
  -latency-log logs/b-latency.jsonl \
  -kcp-ts-debug-log logs/b-kcp-ts.jsonl \
  -kcp-session-stats-log logs/b-kcp-stats.jsonl

Optional ping / echo tools:

./bin/kcpping -id peer-a -server 106.55.173.235:10909 -echo
./bin/kcpping -id peer-b -server 81.70.156.140:10909 -to peer-a -count 20 -interval 100ms
./bin/udpserver -listen 0.0.0.0:9001
./bin/udppeer -id peer-a -server 127.0.0.1:9001
./bin/udpping -id pinger -server 127.0.0.1:9001 -to peer-a -count 20

Python control/video demos use two KCP sessions:

peer-a-ctrl <-> peer-b-ctrl for small binary control packets
peer-b-video -> peer-a-video for larger binary video frames

Example demo entry points:

udp_keyboard_sender.py
udp_xbox_sender.py
udp_fsm_controller.py
omnisocket_video_sender.py
omnisocket_video_receiver.py
scripts/kcp_control_benchmark.py

Python recv_into() note:

The writable buffer must be large enough for the full incoming payload.
If the buffer is too small, recv_into() reports the required size but the current frame has already been consumed and is lost.
For the video demo, keep video_receiver.buffer_bytes >= video_sender.frame_bytes.

Interactive Commands

udppeer and kcppeer support the same interactive shell:

help
text peer-b hello
text peer-a hi
file peer-a /tmp/test125.bin
quit

Notes

The C project targets Linux only.
It preserves the Go wire format for UDP datagrams and KCP stream frames.
It now supports binary payload messages in addition to text, file, register, and error.
Python Session.recv_into() is a zero-copy receive helper for already-sized buffers; it does not retain oversized frames for a retry.
It keeps runtime JSONL logging, UDP TX timestamp debug, KCP packet debug, and KCP session stats.
Offline latencysummary and HTML chart generation are intentionally not migrated.
No automated C tests are included in this subtree; validation is expected to happen on Linux via make and manual smoke tests.