🌐 Network Communication System (dnetwork)

The network communication system handles communication between robots, the game controller, and teammates, enabling team coordination and game rule compliance.

📋 System Overview

The dnetwork module provides two core functions:

GameController Communication: Receive referee commands and game state
Team Communication: Information sharing and coordination between robots

🎮 Game Controller (GameController)

RoboCup SPL Protocol

GameController uses the RoboCup SPL (Standard Platform League) protocol, broadcasting game information via UDP.

Protocol Features:

UDP Port: 3838
Broadcast Frequency: 2 Hz
Data Format: Binary struct

Game States

Game Phases:

python

GAME_STATE = {
    'INITIAL': 0,      # Initial state
    'READY': 1,        # Ready
    'SET': 2,          # Set for kickoff
    'PLAYING': 3,      # Playing
    'FINISHED': 4      # Finished
}

Secondary States:

python

SECONDARY_STATE = {
    'NORMAL': 0,           # Normal play
    'PENALTYSHOOT': 1,     # Penalty shootout
    'OVERTIME': 2,         # Overtime
    'TIMEOUT': 3           # Timeout
}

GCInfo Message

python

GCInfo:
  # Game information
  game_state: 'PLAYING'
  secondary_state: 'NORMAL'
  first_half: True
  kick_off_team: 'blue'

  # Time information
  secs_remaining: 600      # Remaining time (seconds)
  secondary_time: 0

  # Own team information
  team:
    team_number: 17
    team_color: 'blue'
    score: 2
    penalty_shot: 0
    single_shots: 0

    # Robot states
    players:
      - number: 1
        penalty: 'NONE'      # Penalty status
        secs_till_unpenalised: 0
      - number: 2
        penalty: 'NONE'
      # ...

  # Opponent team information
  opponent:
    team_number: 18
    team_color: 'red'
    score: 1
    # ...

Penalty States

python

PENALTY = {
    'NONE': 0,                      # No penalty
    'SPL_ILLEGAL_BALL_CONTACT': 1,  # Illegal ball contact
    'SPL_PLAYER_PUSHING': 2,        # Pushing
    'SPL_ILLEGAL_MOTION_IN_SET': 3, # Illegal motion in SET
    'SPL_INACTIVE_PLAYER': 4,       # Inactive player
    'SPL_ILLEGAL_DEFENDER': 5,      # Illegal defender
    'SPL_LEAVING_THE_FIELD': 6,     # Leaving the field
    'SPL_KICK_OFF_GOAL': 7,         # Kickoff directly into goal
    'SPL_REQUEST_FOR_PICKUP': 8,    # Request for pickup
    'SUBSTITUTE': 14,               # Substitute
    'MANUAL': 15                    # Manual penalty
}

📡 Team Communication

Communication Protocol

Robots broadcast team information using the SPL team communication protocol.

Communication Parameters:

UDP Port: 10000 + team_number
Broadcast Frequency: 10 Hz
Range: Local network

TeamInfo Message

python

TeamInfo:
  # Robot identification
  robot_id: 1
  team_number: 17

  # Position information
  pose:
    x: 1.5       # World coordinates X (meters)
    y: 0.3       # World coordinates Y (meters)
    theta: 0.1   # Heading (radians)

  # Ball information
  ball:
    detected: True
    position: [2.1, 0.5]  # World coordinates
    velocity: [0.1, 0.0]
    timestamp: 1234567890

  # Role information
  role: 'Striker'
  intention: 'chasing_ball'

  # Status
  fallen: False
  battery: 0.85
  timestamp: 1234567890

Teammate Information Access

python

# Get all teammate information
teammates = dnetwork.get_teammates()

for robot in teammates:
    print(f"Robot {robot.robot_id}:")
    print(f"  Position: ({robot.pose.x:.1f}, {robot.pose.y:.1f})")
    print(f"  Role: {robot.role}")
    print(f"  Ball seen: {robot.ball.detected}")

# Get closest teammate
closest = dnetwork.get_closest_teammate(my_position)

🔧 Configuration

Network Configuration

yaml

# dconfig/global.yml
ZJUDancer:
  # Team settings
  TeamNumber: 17                # Team number (must be unique)
  UseGameController: true       # Listen to referee box
  GameControllerAddress: "192.168.1.100"  # Referee box IP

  # Communication settings
  TeamCommunication:
    enabled: true
    port_offset: 10000          # Port = 10000 + TeamNumber
    broadcast_rate: 10          # Hz
    timeout: 2.0                # Teammate data expiry (seconds)

Role Configuration

yaml

# dconfig/global.yml
ZJUDancer:
  # Role configuration
  Role: GCStriker    # GC prefix = listen to GameController
  AttackRight: True  # True = attack right goal, False = attack left
  RobotID: 1        # Robot number

Note

Adding the GC prefix before the role name (e.g., GCStriker) enables GameController command listening. UseGameController must also be set to true.

📊 Using Network Information for Decisions

Ball Information Fusion

When multiple robots see the ball, fuse the information for more accurate estimation:

python

def fuse_ball_position(my_ball, teammates):
    """Fuse ball position from multiple robots"""
    observations = []

    # Add own observation
    if my_ball.detected:
        observations.append({
            'position': my_ball.position,
            'confidence': my_ball.confidence,
            'timestamp': my_ball.timestamp
        })

    # Add teammate observations
    for teammate in teammates:
        if teammate.ball.detected:
            age = current_time() - teammate.ball.timestamp
            if age < 1.0:  # Only use recent data
                observations.append({
                    'position': teammate.ball.position,
                    'confidence': 0.8 * (1 - age),  # Decay with age
                    'timestamp': teammate.ball.timestamp
                })

    if not observations:
        return None

    # Weighted average
    total_weight = sum(o['confidence'] for o in observations)
    fused_x = sum(o['position'][0] * o['confidence'] for o in observations) / total_weight
    fused_y = sum(o['position'][1] * o['confidence'] for o in observations) / total_weight

    return [fused_x, fused_y]

Role Conflict Avoidance

python

def resolve_role_conflict(my_robot, teammates):
    """Resolve role conflicts between robots"""
    strikers = [r for r in teammates if r.role == 'Striker']

    # If already has striker, become supporter
    if strikers and my_robot.role == 'Striker':
        # Keep role for robot closest to ball
        ball_pos = get_ball_position()
        closest_striker = min(strikers, key=lambda r: distance(r.pose, ball_pos))

        if distance(my_robot.pose, ball_pos) > distance(closest_striker.pose, ball_pos):
            my_robot.role = 'Supporter'

🚀 Launch and Configuration

Launch Network Module

bash

# Launch full system (includes network module)
roslaunch dlaunch all.launch robot_id:=1

# Or launch network module separately
roslaunch dnetwork default.launch robot_id:=1

Parameter Setting

bash

# Set robot ID via environment variable
export ZJUDANCER_ROBOTID=1

# Set team number via command line
roslaunch dnetwork default.launch team_number:=17

📊 Monitoring Tools

View GameController Status

bash

# View GC messages
rostopic echo /gc_info

# View message frequency
rostopic hz /gc_info

View Team Information

bash

# View team messages
rostopic echo /team_info

# View all teammate information
rostopic echo /teammates_info

Network Diagnostics

bash

# Check UDP ports
netstat -an | grep 3838
netstat -an | grep 10017

# Test network connectivity
ping <gamecontroller_ip>

📈 Performance Metrics

Metric	Value
GC Receive Frequency	2 Hz
Team Broadcast Frequency	10 Hz
Communication Latency	<50ms
Packet Loss Rate	<1%

Behavior Decision - Using network information for decision making
Configuration Management - Network parameter configuration
Complete Tutorial - Network communication in practice

💡 FAQ

Q: Not receiving GameController messages, what should I do? A: Check network connection, confirm team_number is correctly configured, check firewall settings.

Q: High team communication latency, what should I do? A: Reduce broadcast frequency, reduce message size, check network quality.

Q: How to debug network communication? A: Use Wireshark for packet capture analysis, check ROS logs, use rostopic tools for monitoring.

Q: Multiple robots have role conflicts, what should I do? A: Implement role coordination algorithm, use priority mechanism, periodically synchronize role information.

🌐 Network Communication System (dnetwork) ​

📋 System Overview ​

🎮 Game Controller (GameController) ​

RoboCup SPL Protocol ​

Game States ​

GCInfo Message ​

Penalty States ​

📡 Team Communication ​

Communication Protocol ​

TeamInfo Message ​

Teammate Information Access ​

🔧 Configuration ​

Network Configuration ​

Role Configuration ​

📊 Using Network Information for Decisions ​

Ball Information Fusion ​

Role Conflict Avoidance ​

🚀 Launch and Configuration ​

Launch Network Module ​

Parameter Setting ​

📊 Monitoring Tools ​

View GameController Status ​

View Team Information ​

Network Diagnostics ​

📈 Performance Metrics ​

🔗 Related Documentation ​

💡 FAQ ​

🌐 Network Communication System (dnetwork)

📋 System Overview

🎮 Game Controller (GameController)

RoboCup SPL Protocol

Game States

GCInfo Message

Penalty States

📡 Team Communication

Communication Protocol

TeamInfo Message

Teammate Information Access

🔧 Configuration

Network Configuration

Role Configuration

📊 Using Network Information for Decisions

Ball Information Fusion

Role Conflict Avoidance

🚀 Launch and Configuration

Launch Network Module

Parameter Setting

📊 Monitoring Tools

View GameController Status

View Team Information

Network Diagnostics

📈 Performance Metrics

🔗 Related Documentation

💡 FAQ