Add rate option so sender can restrict outgoing speed

closes #7

connect.go

@@ -28,6 +28,7 @@ type Connection struct {
 	Debug               bool
 	DontEncrypt         bool
 	bars                []*uiprogress.Bar
+	rate                int
 }
 
 type FileMetaData struct {
@@ -46,6 +47,7 @@ func NewConnection(flags *Flags) *Connection {
 	c.Server = flags.Server
 	c.Code = flags.Code
 	c.NumberOfConnections = flags.NumberOfConnections
+	c.rate = flags.Rate
 	if len(flags.File) > 0 {
 		c.File.Name = flags.File
 		c.IsSender = true
@@ -382,7 +384,13 @@ func (c *Connection) sendFile(id int, connection net.Conn) {
 	if !c.Debug {
 		c.bars[id] = uiprogress.AddBar(chunksPerWorker).AppendCompleted().PrependElapsed()
 	}
-	for {
+
+	bufferSizeInKilobytes := BUFFERSIZE / 1024
+	rate := float64(c.rate) / float64(c.NumberOfConnections*bufferSizeInKilobytes)
+	throttle := time.NewTicker(time.Second / time.Duration(rate))
+	defer throttle.Stop()
+
+	for range throttle.C {
 		_, err = file.Read(sendBuffer)
 		if err == io.EOF {
 			//End of file reached, break out of for loop

main.go

@@ -10,6 +10,8 @@ import (
 
 const BUFFERSIZE = 1024
 
+var oneGigabytePerSecond = 1000000 // expressed as kbps
+
 type Flags struct {
 	Relay               bool
 	Debug               bool
@@ -17,6 +19,7 @@ type Flags struct {
 	Server              string
 	File                string
 	Code                string
+	Rate                int
 	NumberOfConnections int
 }
 
@@ -37,6 +40,7 @@ croc version `+version+`
 	flag.StringVar(&flags.Server, "server", "cowyo.com", "address of relay server")
 	flag.StringVar(&flags.File, "send", "", "file to send")
 	flag.StringVar(&flags.Code, "code", "", "use your own code phrase")
+	flag.IntVar(&flags.Rate, "rate", oneGigabytePerSecond, "throttle down to speed in kbps")
 	flag.BoolVar(&flags.DontEncrypt, "no-encrypt", false, "turn off encryption")
 	flag.IntVar(&flags.NumberOfConnections, "threads", 4, "number of threads to use")
 	flag.Parse()