add reuse port (SO_REUSEPORT) example

Author: SimonWaldherr

advanced/reuseport.go

@@ -0,0 +1,39 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/http"
+	"os"
+	"syscall"
+)
+
+var listenConfig = net.ListenConfig{
+	Control: func(network, address string, c syscall.RawConn) error {
+		var opErr error
+		if err := c.Control(func(fd uintptr) {
+			opErr = syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_REUSEPORT, 1)
+		}); err != nil {
+			return err
+		}
+		return opErr
+	},
+}
+
+func main() {
+	pid := os.Getpid()
+	listener, err := listenConfig.Listen(context.Background(), "tcp", "127.0.0.1:8080")
+	if err != nil {
+		panic(err)
+	}
+	server := &http.Server{}
+	http.HandleFunc("/", func(rw http.ResponseWriter, req *http.Request) {
+		rw.WriteHeader(http.StatusOK)
+		fmt.Fprintf(rw, "Hello from PID %d \n", pid)
+		fmt.Printf("serving to %v (%v) with PID %d \n", req.RemoteAddr, req.Header.Get("X-Forwarded-For"), pid)
+	})
+	fmt.Printf("HTTP Server with PID %d is running \n", pid)
+
+	panic(server.Serve(listener))
+}