Merge pull request 'Add VRS JSON format support for readsb integration' (#28) from feature/vrs-json-support into main

Reviewed-on: #28

README.md

@@ -1,12 +1,13 @@
 # SkyView - Multi-Source ADS-B Aircraft Tracker
 
-A high-performance, multi-source ADS-B aircraft tracking application that connects to multiple dump1090 Beast format TCP streams and provides a modern web interface with advanced visualization capabilities.
+A high-performance, multi-source ADS-B aircraft tracking application that connects to multiple dump1090/readsb receivers using Beast binary or VRS JSON formats and provides a modern web interface with advanced visualization capabilities.
 
 ## ✨ Features
 
 ### Multi-Source Data Fusion
-- **Beast Binary Format**: Native support for dump1090 Beast format (port 30005)
+- **Multiple Formats**: Support for both Beast binary (port 30005) and VRS JSON (port 33005) protocols
-- **Multiple Receivers**: Connect to unlimited dump1090 sources simultaneously
+- **Multiple Receivers**: Connect to unlimited dump1090/readsb sources simultaneously
+- **Mixed Sources**: Use Beast and VRS sources together in the same system
 - **Intelligent Merging**: Smart data fusion with signal strength-based source selection
 - **High-throughput Processing**: High-performance concurrent message processing
 
@@ -75,13 +76,25 @@ sudo systemctl enable skyview
   "sources": [
     {
       "id": "primary",
-      "name": "Primary Receiver",
+      "name": "Primary Receiver (Beast)",
       "host": "localhost",
       "port": 30005,
+      "format": "beast",
       "latitude": 51.4700,
       "longitude": -0.4600,
       "altitude": 50.0,
       "enabled": true
+    },
+    {
+      "id": "secondary",
+      "name": "Secondary Receiver (VRS JSON)",
+      "host": "192.168.1.100",
+      "port": 33005,
+      "format": "vrs",
+      "latitude": 51.4800,
+      "longitude": -0.4500,
+      "altitude": 75.0,
+      "enabled": true
     }
   ],
   "settings": {
@@ -97,6 +110,27 @@ sudo systemctl enable skyview
 }
 ```
 
+### Data Format Configuration
+
+SkyView supports two ADS-B data formats:
+
+#### Beast Binary Format
+- **Port**: Typically 30005
+- **Format**: Binary protocol developed by FlightAware
+- **Source**: dump1090, dump1090-fa, readsb with `--net-bo-port 30005`
+- **Configuration**: `"format": "beast"` (default if not specified)
+- **Advantages**: Compact binary format, includes precise timestamps and signal strength
+
+#### VRS JSON Format  
+- **Port**: Typically 33005
+- **Format**: JSON objects with aircraft arrays
+- **Source**: readsb with `--net-vrs-port 33005`
+- **Configuration**: `"format": "vrs"`
+- **Advantages**: Human-readable JSON, simpler to parse and debug
+- **Update Interval**: Configurable with `--net-vrs-interval` (default 5 seconds)
+
+Both formats can be used simultaneously in the same SkyView instance for maximum flexibility and redundancy.
+
 ### Command Line Options
 
 ```bash

cmd/vrs-test/main.go

@@ -0,0 +1,133 @@
+// Package main implements a simple VRS JSON parser test utility.
+//
+// This utility connects to a VRS JSON source and displays the parsed
+// aircraft data for testing and debugging purposes.
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"log"
+	"net"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+
+	"skyview/internal/vrs"
+)
+
+func main() {
+	host := flag.String("host", "svovel", "VRS host to connect to")
+	port := flag.Int("port", 33005, "VRS port to connect to")
+	flag.Parse()
+
+	fmt.Printf("Connecting to VRS JSON source at %s:%d...\n", *host, *port)
+
+	// Connect to VRS source
+	addr := fmt.Sprintf("%s:%d", *host, *port)
+	conn, err := net.DialTimeout("tcp", addr, 30*time.Second)
+	if err != nil {
+		log.Fatalf("Failed to connect to %s: %v", addr, err)
+	}
+	defer conn.Close()
+
+	fmt.Printf("Connected to %s\n", addr)
+
+	// Create VRS parser
+	parser := vrs.NewParser(conn, "test")
+
+	// Set up channels for messages and errors
+	msgChan := make(chan *vrs.VRSMessage, 100)
+	errChan := make(chan error, 10)
+
+	// Set up signal handling
+	ctx, cancel := context.WithCancel(context.Background())
+	sigChan := make(chan os.Signal, 1)
+	signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)
+
+	// Start parsing in background
+	go parser.ParseStream(msgChan, errChan)
+
+	// Statistics tracking
+	messageCount := 0
+	aircraftCount := 0
+	startTime := time.Now()
+
+	fmt.Println("Receiving VRS JSON data... (Press Ctrl+C to stop)")
+	fmt.Println("----------------------------------------")
+
+	for {
+		select {
+		case <-ctx.Done():
+			fmt.Println("\nShutting down...")
+			return
+
+		case <-sigChan:
+			fmt.Println("\nReceived interrupt signal")
+			cancel()
+
+		case err := <-errChan:
+			log.Printf("Parser error: %v", err)
+			cancel()
+
+		case msg := <-msgChan:
+			if msg == nil {
+				cancel()
+				continue
+			}
+
+			messageCount++
+			aircraftCount += len(msg.AcList)
+
+			fmt.Printf("Message %d: %d aircraft\n", messageCount, len(msg.AcList))
+
+			// Display first few aircraft for debugging
+			for i, ac := range msg.AcList {
+				if i >= 3 { // Only show first 3 aircraft per message
+					fmt.Printf("  ... and %d more aircraft\n", len(msg.AcList)-i)
+					break
+				}
+
+				icao, _ := ac.GetICAO24()
+				fmt.Printf("  ICAO: %06X", icao)
+
+				if ac.Call != "" {
+					fmt.Printf("  Call: %-8s", ac.Call)
+				}
+
+				if ac.HasPosition() {
+					fmt.Printf("  Pos: %7.3f°, %8.3f°", ac.Lat, ac.Long)
+				}
+
+				if ac.HasAltitude() {
+					fmt.Printf("  Alt: %5d ft", ac.GetAltitude())
+				}
+
+				if ac.Spd > 0 {
+					fmt.Printf("  Spd: %3.0f kt", ac.Spd)
+				}
+
+				if ac.Trak > 0 {
+					fmt.Printf("  Hdg: %3.0f°", ac.Trak)
+				}
+
+				if ac.Gnd {
+					fmt.Printf("  [GND]")
+				}
+
+				fmt.Printf("  Src: %s\n", ac.GetPositionSource())
+			}
+
+			// Show statistics every 10 messages
+			if messageCount%10 == 0 {
+				elapsed := time.Since(startTime)
+				fmt.Printf("Stats: %d messages, %d total aircraft, %.1fs elapsed\n",
+					messageCount, aircraftCount, elapsed.Seconds())
+			}
+
+			fmt.Println("----------------------------------------")
+		}
+	}
+}

docs/ARCHITECTURE.md

@@ -52,21 +52,28 @@ SkyView is a high-performance, multi-source ADS-B aircraft tracking system built
 
 ## Core Components
 
-### 1. Beast Format Clients (`internal/client/`)
+### 1. Multi-Format Clients (`internal/client/`)
 
-**Purpose**: Manages TCP connections to dump1090 receivers
+**Purpose**: Manages TCP connections to dump1090/readsb receivers using multiple protocols
 
 **Key Features**:
 - Concurrent connection handling for multiple sources
 - Automatic reconnection with exponential backoff
-- Beast binary format parsing
+- Support for Beast binary and VRS JSON formats
 - Per-source connection monitoring and statistics
+- Mixed-format multi-source support
 
 **Files**:
-- `beast.go`: Main client implementation
+- `beast.go`: Beast binary client and multi-source manager
+- `vrs.go`: VRS JSON format client
 
-### 2. Mode S/ADS-B Decoder (`internal/modes/`)
+**Supported Formats**:
+- **Beast Binary**: Traditional binary format from dump1090 (port 30005)
+- **VRS JSON**: JSON format from readsb VRS output (port 33005)
 
+### 2. Data Format Processors
+
+#### Mode S/ADS-B Decoder (`internal/modes/`)
 **Purpose**: Decodes raw Mode S and ADS-B messages into structured aircraft data
 
 **Key Features**:
@@ -78,6 +85,18 @@ SkyView is a high-performance, multi-source ADS-B aircraft tracking system built
 **Files**:
 - `decoder.go`: Core decoding logic
 
+#### VRS JSON Parser (`internal/vrs/`)
+**Purpose**: Parses Virtual Radar Server JSON format aircraft data
+
+**Key Features**:
+- Newline-delimited JSON stream parsing
+- Direct aircraft data extraction (no Mode S decoding required)
+- Support for VRS-specific fields (registration, aircraft type, operator)
+- Position source identification (ADS-B, MLAT, TIS-B, Satellite)
+
+**Files**:
+- `parser.go`: VRS JSON message parsing
+
 ### 3. Data Merger (`internal/merger/`)
 
 **Purpose**: Fuses aircraft data from multiple sources using intelligent conflict resolution
@@ -144,9 +163,9 @@ SkyView is a high-performance, multi-source ADS-B aircraft tracking system built
 ## Data Flow
 
 ### 1. Data Ingestion
-1. **Beast Clients** connect to dump1090 receivers via TCP
+1. **Multi-format Clients** connect to dump1090/readsb receivers via TCP
-2. **Beast Parser** processes binary message stream
+2. **Format Parsers** process binary Beast or JSON VRS message streams
-3. **Mode S Decoder** converts raw messages to structured aircraft data
+3. **Data Converters** convert messages to structured aircraft data (Mode S decoding for Beast, direct mapping for VRS)
 4. **Data Merger** receives aircraft updates with source attribution
 
 ### 2. Data Fusion

internal/client/beast.go

@@ -250,10 +250,10 @@ func (c *BeastClient) processMessages() {
 	}
 }
 
-// MultiSourceClient manages multiple Beast TCP clients for multi-receiver setups.
+// MultiSourceClient manages multiple Beast and VRS clients for multi-receiver setups.
 //
 // This client coordinator:
-//   - Manages connections to multiple Beast format sources simultaneously
+//   - Manages connections to multiple Beast and VRS format sources simultaneously
 //   - Provides unified control for starting and stopping all clients
 //   - Runs periodic cleanup tasks for stale aircraft data
 //   - Aggregates statistics from all managed clients
@@ -262,21 +262,23 @@ func (c *BeastClient) processMessages() {
 // All clients share the same data merger, enabling automatic data fusion
 // and conflict resolution across multiple receivers.
 type MultiSourceClient struct {
-	clients []*BeastClient // Managed Beast clients
+	beastClients []*BeastClient // Managed Beast clients
-	merger  *merger.Merger // Shared data merger for all sources
+	vrsClients   []*VRSClient   // Managed VRS JSON clients
-	mu      sync.RWMutex   // Protects clients slice
+	merger       *merger.Merger // Shared data merger for all sources
+	mu           sync.RWMutex   // Protects client slices
 }
 
-// NewMultiSourceClient creates a client manager for multiple Beast format sources.
+// NewMultiSourceClient creates a client manager for multiple Beast and VRS format sources.
 //
-// The multi-source client enables connecting to multiple dump1090 instances
+// The multi-source client enables connecting to multiple dump1090/readsb instances
-// or other Beast format sources simultaneously. All sources feed into the
+// using either Beast binary or VRS JSON formats simultaneously. All sources feed into
-// same data merger, which handles automatic data fusion and conflict resolution.
+// the same data merger, which handles automatic data fusion and conflict resolution.
 //
 // This is essential for:
 //   - Improved coverage from multiple receivers
 //   - Redundancy in case of individual receiver failures
 //   - Data quality improvement through signal strength comparison
+//   - Support for different receiver output formats
 //
 // Parameters:
 //   - merger: Shared data merger instance for all sources
@@ -284,18 +286,23 @@ type MultiSourceClient struct {
 // Returns a configured multi-source client ready for source addition.
 func NewMultiSourceClient(merger *merger.Merger) *MultiSourceClient {
 	return &MultiSourceClient{
-		clients: make([]*BeastClient, 0),
+		beastClients: make([]*BeastClient, 0),
-		merger:  merger,
+		vrsClients:   make([]*VRSClient, 0),
+		merger:       merger,
 	}
 }
 
-// AddSource registers and configures a new Beast format data source.
+// AddSource registers and configures a new data source (Beast or VRS format).
 //
 // This method:
 //  1. Registers the source with the data merger
-//  2. Creates a new BeastClient for the source
+//  2. Creates appropriate client based on source format
 //  3. Adds the client to the managed clients list
 //
+// The source format is determined by the source.Format field:
+//   - "beast": Creates a BeastClient for Beast binary protocol (default)
+//   - "vrs": Creates a VRSClient for VRS JSON protocol
+//
 // The source is not automatically started; call Start() to begin connections.
 // Sources can be added before or after starting the multi-source client.
 //
@@ -305,18 +312,31 @@ func (m *MultiSourceClient) AddSource(source *merger.Source) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 
+	// Default to Beast format if not specified
+	if source.Format == "" {
+		source.Format = "beast"
+	}
+
 	// Register source with merger
 	m.merger.AddSource(source)
 
-	// Create and start client
+	// Create appropriate client based on format
-	client := NewBeastClient(source, m.merger)
+	switch source.Format {
-	m.clients = append(m.clients, client)
+	case "vrs":
+		client := NewVRSClient(source, m.merger)
+		m.vrsClients = append(m.vrsClients, client)
+	case "beast":
+		fallthrough
+	default:
+		client := NewBeastClient(source, m.merger)
+		m.beastClients = append(m.beastClients, client)
+	}
 }
 
-// Start begins connections to all configured Beast sources.
+// Start begins connections to all configured sources (Beast and VRS).
 //
 // This method:
-//   - Starts all managed BeastClient instances in parallel
+//   - Starts all managed BeastClient and VRSClient instances in parallel
 //   - Begins the periodic cleanup routine for stale aircraft data
 //   - Uses the provided context for cancellation control
 //
@@ -330,7 +350,13 @@ func (m *MultiSourceClient) Start(ctx context.Context) {
 	m.mu.RLock()
 	defer m.mu.RUnlock()
 
-	for _, client := range m.clients {
+	// Start Beast clients
+	for _, client := range m.beastClients {
+		client.Start(ctx)
+	}
+
+	// Start VRS clients
+	for _, client := range m.vrsClients {
 		client.Start(ctx)
 	}
 
@@ -338,7 +364,7 @@ func (m *MultiSourceClient) Start(ctx context.Context) {
 	go m.cleanupRoutine(ctx)
 }
 
-// Stop gracefully shuts down all managed Beast clients.
+// Stop gracefully shuts down all managed clients (Beast and VRS).
 //
 // This method stops all clients in parallel and waits for their
 // goroutines to complete. The shutdown is coordinated to ensure
@@ -347,7 +373,13 @@ func (m *MultiSourceClient) Stop() {
 	m.mu.RLock()
 	defer m.mu.RUnlock()
 
-	for _, client := range m.clients {
+	// Stop Beast clients
+	for _, client := range m.beastClients {
+		client.Stop()
+	}
+
+	// Stop VRS clients
+	for _, client := range m.vrsClients {
 		client.Stop()
 	}
 }
@@ -382,8 +414,8 @@ func (m *MultiSourceClient) cleanupRoutine(ctx context.Context) {
 //
 // The statistics include:
 //   - All merger statistics (aircraft count, message rates, etc.)
-//   - Number of active client connections
+//   - Number of active client connections (Beast and VRS)
-//   - Total number of configured clients
+//   - Total number of configured clients by type
 //   - Per-source connection status and message counts
 //
 // This information is useful for monitoring system health, diagnosing
@@ -397,15 +429,26 @@ func (m *MultiSourceClient) GetStatistics() map[string]interface{} {
 	stats := m.merger.GetStatistics()
 
 	// Add client-specific stats
-	activeClients := 0
+	activeBeastClients := 0
-	for _, client := range m.clients {
+	for _, client := range m.beastClients {
 		if client.source.Active {
-			activeClients++
+			activeBeastClients++
 		}
 	}
 
-	stats["active_clients"] = activeClients
+	activeVRSClients := 0
-	stats["total_clients"] = len(m.clients)
+	for _, client := range m.vrsClients {
+		if client.source.Active {
+			activeVRSClients++
+		}
+	}
+
+	stats["active_beast_clients"] = activeBeastClients
+	stats["active_vrs_clients"] = activeVRSClients
+	stats["active_clients"] = activeBeastClients + activeVRSClients
+	stats["total_beast_clients"] = len(m.beastClients)
+	stats["total_vrs_clients"] = len(m.vrsClients)
+	stats["total_clients"] = len(m.beastClients) + len(m.vrsClients)
 
 	return stats
 }

internal/client/vrs.go

@@ -0,0 +1,350 @@
+// Package client provides VRS JSON format client implementation for connecting to readsb receivers.
+//
+// This file implements a VRS (Virtual Radar Server) JSON format client that connects
+// to readsb instances with --net-vrs-port enabled. VRS JSON is a simpler alternative
+// to the Beast binary protocol, providing aircraft data as JSON over TCP.
+package client
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"sync"
+	"time"
+
+	"skyview/internal/merger"
+	"skyview/internal/modes"
+	"skyview/internal/vrs"
+)
+
+// VRSClient handles connection to a single readsb VRS JSON TCP stream
+//
+// The VRS client provides robust connectivity with:
+//   - Automatic reconnection with exponential backoff
+//   - JSON message parsing and processing
+//   - Integration with data merger
+//   - Source status tracking and statistics
+//   - Graceful shutdown handling
+//
+// VRS JSON is simpler than Beast format but provides the same aircraft data
+type VRSClient struct {
+	source   *merger.Source       // Source configuration and status
+	merger   *merger.Merger       // Data merger for multi-source fusion
+	conn     net.Conn             // TCP connection to VRS source
+	parser   *vrs.Parser          // VRS JSON format parser
+	msgChan  chan *vrs.VRSMessage // Buffered channel for parsed messages
+	errChan  chan error           // Error reporting channel
+	stopChan chan struct{}        // Shutdown signal channel
+	wg       sync.WaitGroup       // Wait group for goroutine coordination
+	
+	// Reconnection parameters
+	reconnectDelay time.Duration // Initial reconnect delay
+	maxReconnect   time.Duration // Maximum reconnect delay (for backoff cap)
+}
+
+// NewVRSClient creates a new VRS JSON format TCP client for a specific data source
+//
+// The client is configured with:
+//   - Buffered message channel (100 messages) for handling updates
+//   - Error channel for connection and parsing issues
+//   - Initial reconnect delay of 5 seconds
+//   - Maximum reconnect delay of 60 seconds (exponential backoff cap)
+//
+// Parameters:
+//   - source: Source configuration including host, port, and metadata
+//   - merger: Data merger instance for aircraft state management
+//
+// Returns a configured but not yet started VRSClient
+func NewVRSClient(source *merger.Source, merger *merger.Merger) *VRSClient {
+	return &VRSClient{
+		source:         source,
+		merger:         merger,
+		msgChan:        make(chan *vrs.VRSMessage, 100),
+		errChan:        make(chan error, 10),
+		stopChan:       make(chan struct{}),
+		reconnectDelay: 5 * time.Second,
+		maxReconnect:   60 * time.Second,
+	}
+}
+
+// Start begins the client connection and message processing in the background
+//
+// The client will:
+//   - Attempt to connect to the configured VRS source
+//   - Handle connection failures with exponential backoff
+//   - Start message reading and processing goroutines
+//   - Continuously reconnect if the connection is lost
+//
+// The method returns immediately; the client runs in background goroutines
+// until Stop() is called or the context is cancelled
+//
+// Parameters:
+//   - ctx: Context for cancellation and timeout control
+func (c *VRSClient) Start(ctx context.Context) {
+	c.wg.Add(1)
+	go c.run(ctx)
+}
+
+// Stop gracefully shuts down the client and all associated goroutines
+//
+// The shutdown process:
+//  1. Signals all goroutines to stop via stopChan
+//  2. Closes the TCP connection if active
+//  3. Waits for all goroutines to complete
+//
+// This method blocks until the shutdown is complete
+func (c *VRSClient) Stop() {
+	close(c.stopChan)
+	if c.conn != nil {
+		c.conn.Close()
+	}
+	c.wg.Wait()
+}
+
+// run implements the main client connection and reconnection loop
+//
+// This method handles the complete client lifecycle:
+//  1. Connection establishment with timeout
+//  2. Exponential backoff on connection failures
+//  3. Message parsing and processing goroutine management
+//  4. Connection monitoring and failure detection
+//  5. Automatic reconnection on disconnection
+//
+// The exponential backoff starts at reconnectDelay (5s) and doubles on each
+// failure up to maxReconnect (60s), then resets on successful connection
+//
+// Source status is updated to reflect connection state for monitoring
+func (c *VRSClient) run(ctx context.Context) {
+	defer c.wg.Done()
+	
+	reconnectDelay := c.reconnectDelay
+	
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-c.stopChan:
+			return
+		default:
+		}
+		
+		// Connect to VRS JSON stream
+		addr := fmt.Sprintf("%s:%d", c.source.Host, c.source.Port)
+		fmt.Printf("Connecting to VRS JSON stream at %s (%s)...\n", addr, c.source.Name)
+		
+		conn, err := net.DialTimeout("tcp", addr, 30*time.Second)
+		if err != nil {
+			fmt.Printf("Failed to connect to VRS source %s: %v\n", c.source.Name, err)
+			c.source.Active = false
+			
+			// Exponential backoff
+			time.Sleep(reconnectDelay)
+			if reconnectDelay < c.maxReconnect {
+				reconnectDelay *= 2
+			}
+			continue
+		}
+		
+		c.conn = conn
+		c.source.Active = true
+		reconnectDelay = c.reconnectDelay // Reset backoff
+		
+		fmt.Printf("Connected to VRS source %s at %s\n", c.source.Name, addr)
+		
+		// Create parser for this connection
+		c.parser = vrs.NewParser(conn, c.source.ID)
+		
+		// Start processing messages
+		c.wg.Add(2)
+		go c.readMessages()
+		go c.processMessages()
+		
+		// Wait for disconnect
+		select {
+		case <-ctx.Done():
+			c.conn.Close()
+			return
+		case <-c.stopChan:
+			c.conn.Close()
+			return
+		case err := <-c.errChan:
+			fmt.Printf("Error from VRS source %s: %v\n", c.source.Name, err)
+			c.conn.Close()
+			c.source.Active = false
+		}
+		
+		// Wait for goroutines to finish
+		time.Sleep(1 * time.Second)
+	}
+}
+
+// readMessages runs in a dedicated goroutine to read VRS JSON messages
+//
+// This method:
+//   - Continuously reads from the TCP connection
+//   - Parses VRS JSON data into Message structs
+//   - Queues parsed messages for processing
+//   - Reports parsing errors to the error channel
+//
+// The method blocks on the parser's ParseStream call and exits when
+// the connection is closed or an unrecoverable error occurs
+func (c *VRSClient) readMessages() {
+	defer c.wg.Done()
+	c.parser.ParseStream(c.msgChan, c.errChan)
+}
+
+// processMessages runs in a dedicated goroutine to process aircraft data
+//
+// For each received VRS message, this method:
+//  1. Iterates through all aircraft in the message
+//  2. Converts VRS format to internal aircraft representation
+//  3. Updates the data merger with new aircraft state
+//  4. Updates source statistics (message count)
+//
+// Invalid or unparseable aircraft data is silently discarded to maintain
+// system stability. The merger handles data fusion from multiple sources
+// and conflict resolution based on signal strength
+func (c *VRSClient) processMessages() {
+	defer c.wg.Done()
+	
+	for {
+		select {
+		case <-c.stopChan:
+			return
+		case msg := <-c.msgChan:
+			if msg == nil {
+				return
+			}
+			
+			// Process each aircraft in the message
+			for _, vrsAircraft := range msg.AcList {
+				// Convert VRS aircraft to internal format
+				aircraft := c.convertVRSToAircraft(&vrsAircraft)
+				if aircraft == nil {
+					continue // Skip invalid aircraft
+				}
+				
+				// Update merger with new data
+				// Note: VRS doesn't provide signal strength, so we use a default value
+				c.merger.UpdateAircraft(
+					c.source.ID,
+					aircraft,
+					-30.0, // Default signal strength for VRS sources
+					vrsAircraft.GetTimestamp(),
+				)
+				
+				// Update source statistics
+				c.source.Messages++
+			}
+		}
+	}
+}
+
+// convertVRSToAircraft converts VRS JSON aircraft to internal aircraft format
+//
+// This method maps VRS JSON fields to the internal aircraft structure used
+// by the merger. It handles:
+//   - ICAO address extraction and validation
+//   - Position data (lat/lon)
+//   - Altitude (barometric and geometric)
+//   - Speed and heading
+//   - Callsign and squawk code
+//   - Ground status
+//
+// Returns nil if the aircraft data is invalid or incomplete
+func (c *VRSClient) convertVRSToAircraft(vrs *vrs.VRSAircraft) *modes.Aircraft {
+	// Get ICAO address
+	icao, err := vrs.GetICAO24()
+	if err != nil {
+		return nil // Invalid ICAO, skip this aircraft
+	}
+	
+	// Create aircraft structure
+	aircraft := &modes.Aircraft{
+		ICAO24: icao,
+	}
+	
+	// Set position if available
+	if vrs.HasPosition() {
+		aircraft.Latitude = vrs.Lat
+		aircraft.Longitude = vrs.Long
+		aircraft.PositionValid = true
+	}
+	
+	// Set altitude if available
+	if vrs.HasAltitude() {
+		aircraft.Altitude = vrs.GetAltitude()
+		aircraft.AltitudeValid = true
+		
+		// Set barometric altitude specifically
+		if vrs.Alt != 0 {
+			aircraft.BaroAltitude = vrs.Alt
+		}
+		
+		// Set geometric altitude if different from barometric
+		if vrs.GAlt != 0 {
+			aircraft.GeomAltitude = vrs.GAlt
+			aircraft.GeomAltitudeValid = true
+		}
+	}
+	
+	// Set speed if available
+	if vrs.Spd > 0 {
+		aircraft.GroundSpeed = int(vrs.Spd)
+		aircraft.GroundSpeedValid = true
+	}
+	
+	// Set heading/track if available
+	if vrs.Trak > 0 {
+		aircraft.Track = int(vrs.Trak)
+		aircraft.TrackValid = true
+	}
+	
+	// Set vertical rate if available
+	if vrs.Vsi != 0 {
+		aircraft.VerticalRate = vrs.Vsi
+		aircraft.VerticalRateValid = true
+	}
+	
+	// Set callsign if available
+	if vrs.Call != "" {
+		aircraft.Callsign = vrs.Call
+		aircraft.CallsignValid = true
+	}
+	
+	// Set squawk if available
+	if squawk, err := vrs.GetSquawk(); err == nil {
+		aircraft.Squawk = fmt.Sprintf("%04X", squawk) // Convert to hex string
+		aircraft.SquawkValid = true
+	}
+	
+	// Set ground status
+	aircraft.OnGround = vrs.IsOnGround()
+	aircraft.OnGroundValid = true
+	
+	// Set selected altitude if available
+	if vrs.TAlt != 0 {
+		aircraft.SelectedAltitude = vrs.TAlt
+	}
+	
+	// Set position source
+	switch vrs.GetPositionSource() {
+	case "MLAT":
+		aircraft.PositionMLAT = true
+	case "TIS-B":
+		aircraft.PositionTISB = true
+	}
+	
+	// Set additional metadata if available
+	if vrs.Reg != "" {
+		aircraft.Registration = vrs.Reg
+	}
+	if vrs.Type != "" {
+		aircraft.AircraftType = vrs.Type
+	}
+	if vrs.Op != "" {
+		aircraft.Operator = vrs.Op
+	}
+	
+	return aircraft
+}

internal/merger/merger.go

@@ -67,6 +67,7 @@ type Source struct {
 	Name      string    `json:"name"`      // Human-readable name
 	Host      string    `json:"host"`      // Hostname or IP address
 	Port      int       `json:"port"`      // TCP port number
+	Format    string    `json:"format"`    // Data format: "beast" or "vrs" (default: "beast")
 	Latitude  float64   `json:"latitude"`  // Receiver location latitude
 	Longitude float64   `json:"longitude"` // Receiver location longitude
 	Altitude  float64   `json:"altitude"`  // Receiver altitude above sea level

internal/modes/decoder.go

@@ -155,6 +155,26 @@ type Aircraft struct {
 	SelectedAltitude int     // MCP/FCU selected altitude in feet
 	SelectedHeading  float64 // MCP/FCU selected heading in degrees
 	BaroSetting      float64 // Barometric pressure setting (QNH) in millibars
+
+	// Additional fields from VRS JSON and extended sources
+	Registration      string // Aircraft registration (e.g., "N12345")
+	AircraftType      string // Aircraft type (e.g., "B738")
+	Operator          string // Airline or operator name
+	
+	// Validity flags for optional fields (used by VRS and other sources)
+	CallsignValid     bool // Whether callsign is valid
+	PositionValid     bool // Whether position is valid
+	AltitudeValid     bool // Whether altitude is valid
+	GeomAltitudeValid bool // Whether geometric altitude is valid
+	GroundSpeedValid  bool // Whether ground speed is valid
+	TrackValid        bool // Whether track is valid
+	VerticalRateValid bool // Whether vertical rate is valid
+	SquawkValid       bool // Whether squawk code is valid
+	OnGroundValid     bool // Whether on-ground status is valid
+
+	// Position source indicators
+	PositionMLAT bool // Position derived from MLAT
+	PositionTISB bool // Position from TIS-B
 }
 
 // Decoder handles Mode S and ADS-B message decoding with CPR position resolution.

internal/vrs/parser.go

@@ -0,0 +1,234 @@
+// Package vrs provides Virtual Radar Server JSON format parsing for ADS-B message streams.
+//
+// The VRS JSON format is a simplified alternative to the Beast binary protocol,
+// providing aircraft data as newline-delimited JSON objects over TCP connections
+// (typically port 33005 when using readsb --net-vrs-port).
+//
+// VRS JSON Format Structure:
+//   - Single-line JSON object per update: {"acList":[{aircraft1},{aircraft2},...]}
+//   - Updates sent at configurable intervals (default 5 seconds)
+//   - Each aircraft object contains ICAO, position, altitude, speed, etc.
+//   - Simpler parsing compared to binary Beast format
+//
+// This package handles:
+//   - JSON message parsing and validation
+//   - Aircraft data extraction from VRS format
+//   - Continuous stream processing with error recovery
+//   - Conversion to internal aircraft data structures
+package vrs
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// VRSMessage represents a complete VRS JSON message containing multiple aircraft
+type VRSMessage struct {
+	AcList []VRSAircraft `json:"acList"`
+}
+
+// VRSAircraft represents a single aircraft in VRS JSON format
+type VRSAircraft struct {
+	Icao  string  `json:"Icao"`  // ICAO hex address (may have ~ prefix for non-ICAO)
+	Lat   float64 `json:"Lat"`   // Latitude
+	Long  float64 `json:"Long"`  // Longitude
+	Alt   int     `json:"Alt"`   // Barometric altitude in feet
+	GAlt  int     `json:"GAlt"`  // Geometric altitude in feet
+	Spd   float64 `json:"Spd"`   // Speed in knots
+	Trak  float64 `json:"Trak"`  // Track/heading in degrees
+	Vsi   int     `json:"Vsi"`   // Vertical speed in feet/min
+	Sqk   string  `json:"Sqk"`   // Squawk code
+	Call  string  `json:"Call"`  // Callsign
+	Gnd   bool    `json:"Gnd"`   // On ground flag
+	TAlt  int     `json:"TAlt"`  // Target altitude
+	Mlat  bool    `json:"Mlat"`  // MLAT position flag
+	Tisb  bool    `json:"Tisb"`  // TIS-B flag
+	Sat   bool    `json:"Sat"`   // Satellite (JAERO) position flag
+	
+	// Additional fields that may be present
+	Reg   string `json:"Reg"`   // Registration
+	Type  string `json:"Type"`  // Aircraft type
+	Mdl   string `json:"Mdl"`   // Model
+	Op    string `json:"Op"`    // Operator
+	From  string `json:"From"`  // Departure airport
+	To    string `json:"To"`    // Destination airport
+	
+	// Timing fields
+	PosTime int64 `json:"PosTime"` // Position timestamp (milliseconds)
+}
+
+// Parser handles VRS JSON format parsing from a stream
+type Parser struct {
+	reader   *bufio.Reader
+	sourceID string
+}
+
+// NewParser creates a new VRS JSON format parser for a data stream
+//
+// Parameters:
+//   - r: Input stream containing VRS JSON data
+//   - sourceID: Identifier for this data source
+//
+// Returns a configured parser ready for message parsing
+func NewParser(r io.Reader, sourceID string) *Parser {
+	return &Parser{
+		reader:   bufio.NewReader(r),
+		sourceID: sourceID,
+	}
+}
+
+// ReadMessage reads and parses a single VRS JSON message from the stream
+//
+// The VRS format sends complete JSON objects on single lines, with each
+// object containing an array of aircraft updates. This is much simpler
+// than Beast binary parsing.
+//
+// Returns the parsed message or an error if the stream is closed or corrupted
+func (p *Parser) ReadMessage() (*VRSMessage, error) {
+	// Read complete line (VRS sends one JSON object per line)
+	line, err := p.reader.ReadString('\n')
+	if err != nil {
+		return nil, err
+	}
+	
+	// Trim whitespace
+	line = strings.TrimSpace(line)
+	if line == "" {
+		// Empty line, try again
+		return p.ReadMessage()
+	}
+	
+	// Parse JSON
+	var msg VRSMessage
+	if err := json.Unmarshal([]byte(line), &msg); err != nil {
+		// Invalid JSON, skip and continue
+		return p.ReadMessage()
+	}
+	
+	return &msg, nil
+}
+
+// ParseStream continuously reads messages from the stream until an error occurs
+//
+// This method runs in a loop, parsing messages and sending them to the provided
+// channel. It handles various error conditions gracefully:
+//   - EOF and closed pipe errors terminate normally (expected on disconnect)
+//   - JSON parsing errors are recovered from automatically
+//   - Other errors are reported via the error channel
+//
+// Parameters:
+//   - msgChan: Channel for sending successfully parsed messages
+//   - errChan: Channel for reporting parsing errors
+func (p *Parser) ParseStream(msgChan chan<- *VRSMessage, errChan chan<- error) {
+	for {
+		msg, err := p.ReadMessage()
+		if err != nil {
+			if err != io.EOF {
+				errChan <- fmt.Errorf("VRS parser error from %s: %w", p.sourceID, err)
+			}
+			return
+		}
+		msgChan <- msg
+	}
+}
+
+// GetICAO24 extracts and cleans the ICAO 24-bit address from VRS format
+//
+// VRS format may prefix non-ICAO addresses with '~'. This method:
+//   - Removes the '~' prefix if present
+//   - Converts hex string to uint32
+//   - Returns 0 for invalid addresses
+func (a *VRSAircraft) GetICAO24() (uint32, error) {
+	// Remove non-ICAO prefix if present
+	icaoStr := strings.TrimPrefix(a.Icao, "~")
+	
+	// Parse hex string
+	icao64, err := strconv.ParseUint(icaoStr, 16, 24)
+	if err != nil {
+		return 0, fmt.Errorf("invalid ICAO address: %s", a.Icao)
+	}
+	
+	return uint32(icao64), nil
+}
+
+// HasPosition returns true if the aircraft has valid position data
+func (a *VRSAircraft) HasPosition() bool {
+	// Check if we have non-zero lat/lon
+	return a.Lat != 0 || a.Long != 0
+}
+
+// HasAltitude returns true if the aircraft has valid altitude data
+func (a *VRSAircraft) HasAltitude() bool {
+	return a.Alt != 0 || a.GAlt != 0
+}
+
+// GetAltitude returns the best available altitude (barometric preferred)
+func (a *VRSAircraft) GetAltitude() int {
+	if a.Alt != 0 {
+		return a.Alt
+	}
+	return a.GAlt
+}
+
+// GetSpeed returns the speed in knots
+func (a *VRSAircraft) GetSpeed() float64 {
+	return a.Spd
+}
+
+// GetHeading returns the track/heading in degrees
+func (a *VRSAircraft) GetHeading() float64 {
+	return a.Trak
+}
+
+// GetVerticalRate returns the vertical speed in feet/min
+func (a *VRSAircraft) GetVerticalRate() int {
+	return a.Vsi
+}
+
+// GetSquawk returns the squawk code as an integer
+func (a *VRSAircraft) GetSquawk() (uint16, error) {
+	if a.Sqk == "" {
+		return 0, fmt.Errorf("no squawk code")
+	}
+	
+	// Parse hex squawk code
+	squawk64, err := strconv.ParseUint(a.Sqk, 16, 16)
+	if err != nil {
+		return 0, fmt.Errorf("invalid squawk code: %s", a.Sqk)
+	}
+	
+	return uint16(squawk64), nil
+}
+
+// GetPositionSource returns the source of position data
+func (a *VRSAircraft) GetPositionSource() string {
+	if a.Mlat {
+		return "MLAT"
+	}
+	if a.Tisb {
+		return "TIS-B"
+	}
+	if a.Sat {
+		return "Satellite"
+	}
+	return "ADS-B"
+}
+
+// GetTimestamp returns the position timestamp as time.Time
+func (a *VRSAircraft) GetTimestamp() time.Time {
+	if a.PosTime > 0 {
+		return time.Unix(0, a.PosTime*int64(time.Millisecond))
+	}
+	// If no timestamp provided, use current time
+	return time.Now()
+}
+
+// IsOnGround returns true if the aircraft is on the ground
+func (a *VRSAircraft) IsOnGround() bool {
+	return a.Gnd
+}