added command line flags
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// =============================================================================
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// Auth: Alex Celani
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// File: led.go
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// Revn: 06-27-2022 1.3
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// Func: receive data as an endpoint, send response back to middleman
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//
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// TODO:
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// =============================================================================
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// CHANGE LOG
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// -----------------------------------------------------------------------------
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// 05-04-2022: init
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// 05-09-2022: began commenting
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// 05-10-2022: finished commenting
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// added alter() and forward()
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// made passed value to alter()/forward() a slice
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// changed refs to recv byte array to slice of n bytes
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// 06-20-2022: changed name to reflect first draft of node.go
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//*06-22-2022: bug squashing and commenting
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// 06-23-2022: updated to produce three different colors
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// 06-26-2022: commented
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// 06-27-2022: added flag package
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//
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// =============================================================================
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package main
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import (
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"net" // ResolveTCPAddr, conn.Write,Read,Close
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// ListenTCP, listener.Accept
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"os" // Args, Stderr, Exit
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"fmt" // Fprintf, Println
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"strings" // ToLower
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"github.com/stianeikeland/go-rpio" // talk to RasPi pins
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"flag" // Parse, String, Int, Bool
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)
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// quick error checking
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func check( err error ) {
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// if user checks an error, it better be nil
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if err != nil {
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// put error in string, print in stderr
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fmt.Fprintf( os.Stderr, "Fatal error: %s", err.Error() )
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os.Exit( 2 ) // quit
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}
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}
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// parse incoming message, keep only second word
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func parse( recv string ) string {
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// split message over spaces
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keywords := strings.Split( recv, " " )
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return keywords[1] // return the second word
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}
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// function to handle incoming connections
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func handleClient( conn net.Conn ) {
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defer conn.Close() // barring any error, still close connection
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var buf [512]byte // declare large byte array, store messages
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// iterate forever to always read over connection
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for {
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// read n bytes from connection into buffer
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n, err := conn.Read( buf[0:] )
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if err != nil { // erroring on read will simply leave the
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return // function so it can start again later
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}
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if *verbose {
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// print recv'd message
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// string() only works on byte SLICES so [:] is required
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fmt.Println( "recv: ", string( buf[:n] ) )
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}
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// split command into words for ease of parsing
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command := strings.Split( string( buf[:n] ), " " )
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if command[1] != "led" { // confirm message belongs here
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os.Exit( 2 ) // if not, exit
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}
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var resp string // declare response variable
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// TODO convert to switches?
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// len is 3 for "asK" commands
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if len( command ) == 3 {
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if command[2] == "color" {
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// if user wants color, return color
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resp = color
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} else if command[2] == "status" {
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// if user wants status, return status
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resp = status
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} else {
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// there are only those two fields
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resp = "usage unknown"
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}
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// len is 4 for tell commands
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} else if len( command ) == 4 {
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// if user wants to set color
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if command[2] == "color" {
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color = command[3] // set current color
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resp = color // return current color
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switch color {
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case "blue": // does user want blue?
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// turn blue on, turn rest off
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pinB.High()
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pinR.Low()
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pinG.Low()
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case "red": // does user want red?
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// turn red on, turn rest off
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pinB.Low()
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pinR.High()
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pinG.Low()
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case "green": // does user want green?
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// turn green on, turn rest off
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pinB.Low()
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pinR.Low()
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pinG.High()
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default: // color unknown
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// turn off
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pinB.Low()
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pinR.Low()
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pinG.Low()
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}
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// if user wants to set status
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} else if command[2] == "status" {
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status = command[3] // set current status
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resp = status // return current status
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switch status {
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case "on": // does user want on?
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// default to red
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pinB.Low()
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pinR.High()
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pinG.Low()
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default: // anything else, like off
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// default to off
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pinB.Low()
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pinR.Low()
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pinG.Low()
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}
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// user entered something else entirely
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} else {
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resp = "usage unknown"
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}
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// no other lengths are valid
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} else {
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os.Exit( 2 ) // exit in this case
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}
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if *verbose {
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fmt.Println( "answer: ", resp ) // print response
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}
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// write that response back to original client
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_, err = conn.Write( []byte( resp ) )
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if err != nil { // erroring on write will simply leave the
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return // function so it can start again later
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}
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if *verbose {
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fmt.Println( "sent: ", resp ) // print response
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}
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}
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}
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//var params = make( map[string]string )
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//var states = make( map[string]string )
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var pinR rpio.Pin // declare red led pin
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var pinG rpio.Pin // declare green led pin
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var pinB rpio.Pin // declare blue led pin
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var color string // declare color variable
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var status string // declare status variable
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var ( // declare flag variables
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lr *int
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lg *int
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lb *int
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verbose *bool
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ip *string
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)
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func main() {
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// declare command line input variables
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lr = flag.Int( "lr", 11, "GPIO pin for red LED" )
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lg = flag.Int( "lg", 9, "GPIO pin for green LED" )
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lb = flag.Int( "lb", 25, "GPIO pin for blue LED" )
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verbose = flag.Bool( "v", false, "verbose printing" )
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ip = flag.String( "ip", ":1202", "ip and port of self" )
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flag.Parse()
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// initialize pins to GPIO 11, 9, and 25
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pinR = rpio.Pin( *lr )
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pinG = rpio.Pin( *lg )
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pinB = rpio.Pin( *lb )
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if err := rpio.Open(); err != nil {
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// on error, print error and exit
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fmt.Println(err)
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os.Exit(1)
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}
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// Unmap gpio memory when done
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defer rpio.Close()
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// Set pins to output mode
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pinR.Output()
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pinG.Output()
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pinB.Output()
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// "resolve" ip & host according to TCP rules
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tcpAddr, err := net.ResolveTCPAddr( "tcp", *ip )
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check( err ) // check error
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// bind and "listen" to ip and port, according to tcp rules
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listener, err := net.ListenTCP( "tcp", tcpAddr )
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check( err ) // check error
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// iterate forever
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// TODO i mean i can totally make this more user friendly
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for {
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// accept a connection that makes its way to bound port
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conn, err := listener.Accept()
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if err != nil { // if connection fails...
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continue // don't quit program, not fatal error
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}
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// asynchronous function to handle connection to client
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go handleClient( conn )
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}
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}
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