# OmniSocketC

Linux-only C11 implementation of the UDP/KCP transport stack from `OmniSocketGo`.

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

```bash
make -j$(nproc)
```

Build outputs:

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

Python extension build:

```bash
make python-ext
make python-install
```

## Run On Different Machines

Server `D` runs the KCP hub on `0.0.0.0:10909`:

```bash
./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`:

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

Peer `A` dials `D` through relay `C`:

```bash
./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:

```bash
./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:

```bash
./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:

```text
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.