Documentation for TCP Server Application in Go

Overview

This Go program is a crucial component of our infrastructure, being the only program that runs directly on the robot. It implements a TCP server that listens for incoming connections on a specified port and handles JSON messages for controlling motors, lightbars, and a buzzer. Additionally, it manages health checks to monitor the connection’s status.

Structure and Functionality

Main Components

  • Motor: Represents a motor with its control values.
  • Lightbar: Represents a lightbar with various attributes like mode, color, effect, and speed.
  • Buzzer: Represents a buzzer with a duration attribute.

Global Variables

  • motorChan, lightbarChan, buzzerChan: Channels for passing motor, lightbar, and buzzer data.
  • rosmaster: Instance of rosmasterlib.Rosmaster, used to set motor and lightbar states and control the buzzer.

Main Function

  1. TCP Server Setup: Initializes a TCP server listening on a user-defined port.
  2. Signal Handling: Captures OS signals for graceful shutdown.
  3. JSON Handler: Runs a goroutine to handle incoming JSON messages for motor, lightbar, and buzzer.
  4. Connection Handling: Accepts incoming connections and processes data sent by clients.

JSON Message Handling (handleIncomingJson)

Processes incoming JSON messages from the channels and updates the state of motors, lightbars, and the buzzer accordingly.

Health Check Routine (handleHealthcheck)

Monitors the health of the connection and triggers a shutdown if no health check message is received within a specified time frame.

Connection Management (handleConnection)

  1. Command Processing: Interprets and acts upon commands received from the client, such as starting or stopping streams.
  2. Stream Handling: Manages streams for camera, lidar, and battery data.
  3. Health Check Integration: Incorporates the health check routine to monitor connection integrity.

Utility Functions

  • threeBeep(): Triggers the buzzer to beep three times.
  • closeAllChannels(chans ...chan struct{}): Closes all provided channels.
  • logWithTimestamp(v ...interface{}): Logs messages with a timestamp.

Usage

To run the server:

  1. Compile and Run: Compile the Go code and run the resulting binary. Optionally, specify the port to listen on using the -port flag.
  2. Client Connection: Connect a client to the server’s IP and port.
  3. Data Transmission: The client can send JSON-formatted messages to control motors, lightbars, and buzzers, and send commands to start/stop data streams.

Compiling for Different Architectures and Operating Systems

To compile the Go program for a different architecture or operating system, use the GOOS and GOARCH environment variables. For example:

  • To compile for Windows on an AMD64 architecture: 
    GOOS=windows GOARCH=amd64 go build
  • To compile for Linux on an ARM64 architecture, which is what we need for the robot: 
    GOOS=linux GOARCH=arm64 go build

Replace the values of GOOS and GOARCH as needed to target the desired platform.

Notes

  • Ensure that the rosmasterlib and streamhandlers packages are correctly imported and configured.
  • Proper error handling and logging are implemented for robustness.
  • The program is designed to run indefinitely until an interrupt signal is received.

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