lossy
Go package to simulate bandwidth, latency and packet loss for net.PacketConn and net.Conn interfaces.
Its main usage is to test robustness of applications and network protocols run over unreliable transport protocols such as UDP or IP.
As a side benefit, it can also be used as outbound bandwidth limiter.
lossy only alters the writing side of the connection, reading side is kept as it is.
Example
package main
import (
"fmt"
"github.com/cevatbarisyilmaz/lossy"
"log"
"math/rand"
"net"
"time"
)
const packetSize = 64
func main() {
// Create two connection endpoints over UDP
packetConn, conn := createConnections()
// Create a lossy packet connection
bandwidth := 1048 // 8 Kbit/s
minLatency := 100 * time.Millisecond
maxLatency := time.Second
packetLossRate := 0.33
headerOverhead := lossy.UDPv4MinHeaderOverhead
lossyPacketConn := lossy.NewPacketConn(packetConn, bandwidth, minLatency, maxLatency, packetLossRate, headerOverhead)
// Write some packets via lossy
var bytesWritten int
const packetCount = 32
go func() {
for i := 0; i < packetCount; i++ {
packet := createPacket()
_, err := lossyPacketConn.WriteTo(packet, conn.LocalAddr())
if err != nil {
log.Fatal(err)
}
bytesWritten += len(packet) + headerOverhead
}
fmt.Println("Sent", packetCount, "packets with total size of", bytesWritten, "bytes")
baseTransmissionDuration := time.Duration(float64(bytesWritten * int(time.Second)) / float64(bandwidth))
earliestCompletion := baseTransmissionDuration + minLatency
latestCompletion := baseTransmissionDuration + maxLatency
fmt.Println("Expected transmission duration is between", earliestCompletion, "and", latestCompletion)
}()
// Read packets at the other side
const timeout = 3 * time.Second
var packets, bytesRead int
startTime := time.Now()
for {
_ = conn.SetReadDeadline(time.Now().Add(timeout))
buffer := make([]byte, packetSize)
n, err := conn.Read(buffer)
if err != nil {
break
}
bytesRead += n + headerOverhead
packets++
}
dur := time.Now().Sub(startTime) - timeout
fmt.Println("Received", packets, "packets with total size of", bytesRead, "bytes in", dur)
// Close the connections
_ = lossyPacketConn.Close()
_ = conn.Close()
}
func createConnections() (net.PacketConn, net.Conn) {
packetConn, err := net.ListenUDP("udp", &net.UDPAddr{
IP: net.IPv4(127, 0, 0, 1),
Port: 0,
})
if err != nil {
log.Fatal(err)
}
conn, err := net.DialUDP("udp", nil, packetConn.LocalAddr().(*net.UDPAddr))
if err != nil {
log.Fatal(err)
}
return packetConn, conn
}
func createPacket() []byte {
packet := make([]byte, packetSize)
rand.Read(packet)
return packet
}
Output
Sent 32 packets with total size of 2944 bytes
Expected transmission duration is between 2.909160305s and 3.809160305s
Received 23 packets with total size of 2116 bytes in 3.2507523s