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ETCP Monitor - Implementation Summary

Overview

ETCP Monitor is a Windows GUI utility for real-time monitoring of ETCP connections in uTun.

Architecture

Protocol (Binary)

Format: [2 bytes: size] [1 byte: type] [payload...]
Period: 100ms updates
Transport: TCP socket

Message Types

Client → Server:

0x01 - Request connection list
0x02 - Select connection by peer_node_id
0x03 - Request metrics
0x04 - Disconnect

Server → Client:

0x81 - Connection list response
0x82 - Metrics response (ETCP + TUN + Links)
0xFF - Error response

Files Created

Protocol (Shared)

tools/etcpmon/etcpmon_protocol.h - Protocol definitions and structures

Server (uTun)

src/control_server.h - Control server interface
src/control_server.c - TCP server implementation
Modified src/utun_instance.c - Integration with uTun lifecycle
Modified src/Makefile.am - Added control_server.c to build
Modified lib/debug_config.h - Added DEBUG_CATEGORY_CONTROL

Client (Windows GUI)

tools/etcpmon/etcpmon_client.h/c - Network layer (Winsock)
tools/etcpmon/etcpmon_gui.h/c - WinAPI GUI implementation
tools/etcpmon/etcpmon_main.c - Entry point
tools/etcpmon/Makefile.mingw - MinGW build
tools/etcpmon/build.bat - Windows build script
tools/etcpmon/build.sh - Unix build script
tools/etcpmon/clean.bat - Clean script
tools/etcpmon/README.md - Documentation

Test

tests/test_control_server.c - Integration test for control server protocol

Library Fix

lib/u_async.c - Modified to use select() on Windows instead of WSAPoll

Build Instructions

Windows (Recommended)

cd tools\etcpmon
build.bat

Unix/MinGW

cd tools/etcpmon
bash build.sh

Usage

1. Configure uTun

Add to utun.conf:

control_ip=127.0.0.1
control_port=9090

2. Start uTun

./utun

3. Start ETCP Monitor

etcpmon.exe

4. Connect

Enter server IP:port (default: 127.0.0.1:9090)
Click "Connect"
Select connection from list
View real-time metrics

Metrics Displayed

ETCP Connection

RTT (last, avg 10, avg 100)
Jitter
Bytes sent total
Retransmission count
ACK count
Unacked bytes
Links count

TUN Interface

Bytes read/written
Packets read/written
Read/write errors

Links (per link)

Status (UP/DOWN)
Encrypt/decrypt errors
Send/receive errors
Total encrypted/decrypted bytes
Bandwidth (Kbps)
NAT changes count

Technical Details

Windows select() Implementation

On Windows, the uasync library now uses select() instead of WSAPoll() for socket monitoring. This resolves issues with accepted TCP sockets that caused WSAPoll to fail with error 10022 (WSAEINVAL).

Changes in lib/u_async.c:

Added Windows-specific code path using select()
Maintains compatibility with Linux (uses poll())
Properly handles both regular FDs and socket_t types

Binary Protocol

The protocol uses fixed-size binary structures for efficient communication:

Header: 3 bytes (2 size + 1 type)
Connection list item: 40 bytes (8 peer_id + 32 name)
ETCP metrics: 40 bytes
Link metrics: 32 bytes per link
TUN metrics: 24 bytes

Testing

Unit Test

cd tests
./test_control_server

Expected output:

================================
Control Server Protocol Test
================================

[TEST] Setting up mock data...
[TEST] Mock data ready (1 conn, 2 links)
[TEST] Starting control server on port 19090...
[TEST] Control server started ✓
[TEST] Starting client thread...
[TEST] Running event loop...

[CLIENT] Connecting to 127.0.0.1:19090...
[CLIENT] Connected
[CLIENT] Sending CMD_LIST_CONN...
[CLIENT] Waiting for response...
[CLIENT] Received connection list: 1 connection(s)
[CLIENT] Connection verified: peer_id=0x1234567890ABCDEF ✓
[CLIENT] All tests passed ✓

[TEST] Cleaning up...

================================
[PASS] All tests passed!
================================

License

See main project LICENSE file.

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