145 lines
4.6 KiB
Go
145 lines
4.6 KiB
Go
// =============================================================================
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// Auth: Alex Celani
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// File: gps.go
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// Revn: 07-25-2023 3.0
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// Func: asynchronously receive messages from another program, print
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//
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// TODO: add LED
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// add flags
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// =============================================================================
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// CHANGE LOG
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// -----------------------------------------------------------------------------
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//*07-13-2023: copied over, removed call to alter()/forward()
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// removed any call to write
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// put read and print in a for loop
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// wrote getFileName() to create a filename based off
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// current time
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// write output to a logfile
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// moved file writing to AFTER checking for fin
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//*07-20-2023: added calls to os.Create(), file.Write(), etc
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// 07-21-2023: tested filewriting stuff, no avail
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// 07-24-2023: added bufio import and buffered file writing
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//*07-25-2023: commented bufio stuffs
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//
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// =============================================================================
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package main
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import (
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"bufio" // NewWriter, Write, Writer.Flush
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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, Create, Write, Close,
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// WriteString
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"fmt" // Fprintf, Println
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"strings" // ToLower, Compare
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"time" // Now, Format
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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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func getFileName() string{
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// capture current time
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t := time.Now()
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// format as YYYYMMDDHHmmss.gps
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return t.Format( "20060102150405" ) + ".gps"
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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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// debug printing stuff
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// fmt.Println( "handling" )
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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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// print recv'd message
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// string() only works on byte SLICES so [:] is required
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// debug print
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// fmt.Println( "recv: ", string( buf[:n] ) )
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// essentially a case statement for conn.Read, Compare makes
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// it hard to do that
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// check to see if buf[:n] is start
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if strings.Compare( string( buf[:n] ), "start" ) == 0 {
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filename := getFileName() // get name of file
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file, err = os.Create( filename ) // create new file
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check( err ) // make sure file creation worked
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writer = bufio.NewWriter( file ) // create filewriter
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// check to see if buf[:n] is fin
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} else if strings.Compare( string( buf[:n] ), "fin" ) == 0 {
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// debug print
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// fmt.Println( "premature file closing" )
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file.Close() // close file
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// possibly strike exit...
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os.Exit( 2 ) // quit
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// if conn.Read is not start or fin, it's data
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} else {
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// write info to file
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_, err = writer.Write( buf[:n] )
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check( err ) // make sure write worked
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err = writer.Flush() // flush write to file
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check( err ) // make sure write worked
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// debug print
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// fmt.Println( "writing" )
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}
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}
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}
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var file *os.File
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var writer *bufio.Writer
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func main() {
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// ip:port
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// ip doesn't exist, implies localhost
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service := ":1202" // capture ip address and host
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// "resolve" ip & host according to TCP rules
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tcpAddr, err := net.ResolveTCPAddr( "tcp", service )
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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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