techircd/docs/CONNECTION_HANDLING.md

# TechIRCd Connection Handling Improvements

## Overview
TechIRCd now features **robust connection handling** designed to handle real-world network conditions, client behaviors, and edge cases gracefully.

## Key Improvements

### 🛡️ **Robust Client Connection Handling**

#### **1. Comprehensive Error Recovery**
- **Panic Recovery**: All client handlers have panic recovery with detailed logging
- **Graceful Cleanup**: Proper resource cleanup even when connections fail
- **Connection Validation**: Validates connections and server state before processing

#### **2. Smart Timeout Management**
- **Registration Timeout**: 60 seconds for initial registration (configurable)
- **Read Timeouts**: 5 minutes for registered clients, 30 seconds during registration
- **Progressive Timeouts**: More lenient timeouts for new connections

#### **3. Enhanced Message Processing**
- **Binary Data Detection**: Detects and rejects non-text data
- **Size Limits**: Truncates oversized messages (512 bytes max)
- **Empty Line Handling**: Gracefully ignores empty lines
- **Encoding Validation**: Checks for valid IRC characters

#### **4. Intelligent Flood Protection**
- **Registration Leniency**: More generous limits during connection setup
- **Sliding Window**: Proper flood detection with time windows
- **Configurable Limits**: Respects server configuration settings

### 🔧 **Server Connection Management**

#### **1. Connection Limits**
- **Max Client Enforcement**: Rejects connections when server is full
- **Resource Protection**: Prevents server overload
- **Graceful Rejection**: Sends proper error message before closing

#### **2. Accept Error Handling**
- **Temporary Error Recovery**: Handles temporary network errors
- **Retry Logic**: Continues accepting after temporary failures
- **Error Classification**: Different handling for different error types

#### **3. Client State Tracking**
- **Connection Counting**: Real-time client count tracking
- **State Validation**: Ensures clients are properly initialized
- **Resource Monitoring**: Tracks and logs connection statistics

### 📊 **Enhanced Logging and Debugging**

#### **1. Detailed Connection Logging**
```
2025/09/03 19:02:44 New client connected from 46.24.193.29:60237 (total: 1)
2025/09/03 19:02:44 Starting robust client handler for 46.24.193.29:60237
2025/09/03 19:02:44 Client 46.24.193.29:60237: CAP LS 302
2025/09/03 19:02:44 Client 46.24.193.29:60237: NICK TestUser
2025/09/03 19:02:44 Client registration completed: TestUser (testuser) from 46.24.193.29:60237
```

#### **2. Error Context**
- **Connection Source**: Always logs client IP/port
- **Error Details**: Specific error messages for troubleshooting
- **State Information**: Logs registration status and timing

#### **3. Performance Metrics**
- **Connection Duration**: Tracks how long connections last
- **Message Counts**: Monitors message frequency
- **Registration Time**: Measures time to complete registration

### 🔒 **Security Enhancements**

#### **1. Protocol Validation**
- **Command Validation**: Ensures only valid IRC commands are processed
- **Data Sanitization**: Removes dangerous or malformed input
- **Buffer Management**: Prevents buffer overflow attacks

#### **2. Connection Security**
- **Rate Limiting**: Prevents rapid connection attempts
- **Resource Limits**: Protects against resource exhaustion
- **Input Validation**: Validates all client input before processing

### 🚀 **Real-World Compatibility**

#### **1. IRC Client Support**
- **HexChat Compatible**: Tested with popular IRC clients
- **IRCv3 Support**: Handles capability negotiation properly
- **Standard Compliance**: Follows RFC 2812 standards

#### **2. Network Conditions**
- **Slow Connections**: Handles high-latency connections
- **Unstable Networks**: Recovers from temporary network issues
- **Mobile Clients**: Optimized for mobile network conditions

#### **3. Edge Cases**
- **Partial Messages**: Handles incomplete message transmission
- **Connection Drops**: Graceful handling of sudden disconnections
- **Server Restarts**: Proper cleanup during server shutdown

## Configuration Options

### **Timeout Settings**
```json
{
  "limits": {
    "registration_timeout": 60,
    "ping_timeout": 300,
    "flood_lines": 10,
    "flood_seconds": 60
  }
}
```

### **Connection Limits**
```json
{
  "limits": {
    "max_clients": 1000,
    "max_channels": 100
  }
}
```

## Benefits

### **For Users**
- ✅ **Reliable Connections**: Less likely to drop due to network issues
- ✅ **Faster Registration**: Optimized registration process
- ✅ **Better Error Messages**: Clear feedback when issues occur
- ✅ **Mobile Friendly**: Works well on mobile networks

### **For Administrators**
- ✅ **Detailed Logging**: Easy troubleshooting with comprehensive logs
- ✅ **Resource Protection**: Server stays stable under load
- ✅ **Security**: Protection against malformed data and attacks
- ✅ **Monitoring**: Real-time connection statistics

### **For Developers**
- ✅ **Code Clarity**: Well-structured connection handling code
- ✅ **Error Recovery**: Robust error handling prevents crashes
- ✅ **Debugging**: Extensive logging for issue resolution
- ✅ **Maintainability**: Clean separation of concerns

## Testing Recommendations

### **Basic Connection Test**
```bash
# Test with telnet
telnet your-server.com 6667

# Send IRC commands
NICK TestUser
USER testuser 0 * :Test User
```

### **HexChat Configuration**
- **Server**: your-server.com
- **Port**: 6667 (or 6697 for SSL)
- **SSL**: Disabled (unless you have SSL configured)
- **Character Set**: UTF-8

### **Load Testing**
- Test with multiple simultaneous connections
- Try rapid connect/disconnect cycles
- Test with slow network conditions

TechIRCd now provides **enterprise-grade connection handling** suitable for production IRC networks!