go udp requests (packet) loss - go

Question

i wrote simple server and client for tcp and udp connection
package main
//server.go
import (
"fmt"
"net"
"os"
"os/signal"
"syscall"
)
func main() {
tcp := 0
udp := 0
defer func(o, t *int) {
fmt.Println(*o, *t)
}(&tcp, &udp)
go func() {
l, err := net.ListenTCP("tcp", &net.TCPAddr{
IP: net.ParseIP("0.0.0.0"),
Port: 3000,
})
if err != nil {
panic(err)
}
b := make([]byte, 24)
for {
conn, err := l.Accept()
if err != nil {
continue
}
n, err := conn.Read(b)
if err != nil {
continue
}
r := string(b[:n])
if r == "close" {
conn.Close()
break
} else {
_, err = conn.Write([]byte("pong"))
if err != nil {
continue
}
}
conn.Close()
tcp++
}
l.Close()
}()
go func() {
conn, err := net.ListenUDP("udp", &net.UDPAddr{
IP: net.ParseIP("0.0.0.0"),
Port: 3000,
})
if err != nil {
panic(err)
}
b := make([]byte, 24)
for {
n, addr, err := conn.ReadFromUDP(b)
if err != nil {
continue
}
r := string(b[:n])
if r == "close" {
break
} else {
_, err = conn.WriteToUDP([]byte("pong"), addr)
if err != nil {
continue
}
}
udp++
}
conn.Close()
}()
signals := make(chan os.Signal, 1)
signal.Notify(signals, os.Interrupt, syscall.SIGTERM)
<-signals
}
package main
//client.go
import (
"fmt"
"net"
"os"
"os/signal"
"strconv"
"sync/atomic"
"syscall"
"time"
)
func main() {
t := "tcp"
m := "ping"
c := 1
if len(os.Args) > 1 {
t = os.Args[1]
}
if len(os.Args) > 2 {
m = os.Args[2]
}
if len(os.Args) > 3 {
c, _ = strconv.Atoi(os.Args[3])
}
tcp := int64(0)
udp := int64(0)
defer func(o, t *int64) {
fmt.Println(*o, *t)
}(&tcp, &udp)
if c == 1 {
if t == "tcp" {
addr, err := net.ResolveTCPAddr("tcp", ":3000")
if err != nil {
panic(err)
}
conn, err := net.DialTCP("tcp", nil, addr)
if err != nil {
panic(err)
}
_, err = conn.Write([]byte(m))
if err != nil {
panic(err)
}
tcp++
}
if t == "udp" {
addr, err := net.ResolveUDPAddr("udp", ":3000")
if err != nil {
panic(err)
}
conn, err := net.DialUDP("udp", nil, addr)
if err != nil {
panic(err)
}
_, err = conn.Write([]byte(m))
if err != nil {
panic(err)
}
udp++
}
os.Exit(0)
}
for i := 0; i < c; i++ {
go func() {
a1, err := net.ResolveTCPAddr("tcp", ":3000")
if err != nil {
panic(err)
}
c1, err := net.DialTCP("tcp", nil, a1)
if err != nil {
panic(err)
}
_, err = c1.Write([]byte(m))
if err != nil {
panic(err)
}
buf := make([]byte, 24)
n, err := c1.Read(buf)
if err != nil {
panic(err)
}
if string(buf[:n]) != "pong" {
panic(1)
}
err = c1.Close()
if err != nil {
panic(err)
}
g := atomic.AddInt64(&tcp, 1)
if g % 100 == 0 {
fmt.Println("tcp", g)
time.Sleep(time.Millisecond * 1000)
}
}()
go func() {
a2, err := net.ResolveUDPAddr("udp", ":3000")
if err != nil {
panic(err)
}
c2, err := net.DialUDP("udp", nil, a2)
if err != nil {
panic(err)
}
_, err = c2.Write([]byte(m))
if err != nil {
panic(err)
}
buf := make([]byte, 24)
n, err := c2.Read(buf)
if err != nil {
panic(err)
}
if string(buf[:n]) != "pong" {
panic(1)
}
err = c2.Close()
if err != nil {
panic(err)
}
g := atomic.AddInt64(&udp, 1)
if g % 100 == 0 {
fmt.Println("udp", g)
time.Sleep(time.Millisecond * 1000)
}
}()
}
signals := make(chan os.Signal, 1)
signal.Notify(signals, os.Interrupt, syscall.SIGTERM)
<-signals
}
and get a strange behavior: not all udp requests are sent or handled on many connections.
When i sent 100 or 200 both server and client tells me that all requests worked but from 1000 there is a strange ~5% requests loss on udp for both server and client but no panic.
I know udp allows packet loss but 5% on localhost requests seems like an error.

Answer 1

As we know, the UDP is connectionless, so packet loss may be caused by this nature of UDP. There could be several ways to lower the rate of packet loss.
Slow down the rate of packets sent on the client side
Call SetWriteBuffer to increase the buffer size on the client side and set SetReadBuffer to increase the buffer size on the server side
conn, err := net.DialUDP("udp", nil, addr)
err = conn.SetWriteBuffer(64 * 1024 * 1024)
Check the system network information through netstat -s -udp and get UDP statistics information. You could try to change the default value of rmem_max and rmem_default on the server side. For more details, please refer to 1 and 2