lossy

有損的

Go package 可以模擬 net.PacketConn 和 net.Conn 介面的頻寬、延遲和封包遺失。

其主要用途是測試在不可靠的傳輸協定（例如 UDP 或 IP）上運行的應用程式和網路協定的穩健性。作為一個附帶好處，它也可以用作出站頻寬限制器。

有損僅改變連接的寫入側，讀取側保持原樣。

例子

 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
}

輸出

 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