go: first example using Go

README.md

@@ -16,6 +16,7 @@ The following examples show how enable Multipath TCP with different programming
  - [Using Multipath TCP in python](python/README.md)
  - [Using Multipath TCP in perl](perl/README.md)
  - [Using Multipath TCP in Rust](rust/README.md)
+ - [Using Multipath TCP in Go](go/README.md)
 
 
 

go/README.md

@@ -0,0 +1,14 @@
+# Using Multipath TCP in Go
+
+To use Multipath TCP in Go, you can create the socket manually with syscalls
+like you would do in other languages but this is not an usual and practical way.
+
+Instead, from Go 1.21, MPTCP support has been added in the net package:
+
+- https://go.dev/issue/56539
+- https://go.dev/issue/59166
+
+Examples:
+
+- [simple client](mptcp-client.go)
+- [simple server](mptcp-server.go)

go/mptcp-client.go

@@ -0,0 +1,38 @@
+package main
+
+import (
+	"log"
+	"net"
+	"os"
+	"time"
+)
+
+func main() {
+	addr := os.Args[1]
+
+	d := &net.Dialer{}
+	d.SetMultipathTCP(true)
+	conn, err := d.Dial("tcp", addr)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer conn.Close()
+
+	tcp, ok := conn.(*net.TCPConn)
+	if !ok {
+		log.Fatal("struct is not a TCPConn")
+	}
+
+	/* This API is still under discussion: https://go.dev/issue/59166
+	mptcp, err := tcp.MultipathTCP()
+	if err != nil {
+		log.Fatal(err)
+	}
+	*/mptcp := tcp != nil
+
+	log.Printf("connection to %s mptcp %t", addr, mptcp)
+
+	time.Sleep(time.Second)
+
+	conn.Close()
+}

go/mptcp-server.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"context"
+	"log"
+	"net"
+	"os"
+)
+
+func main() {
+	addr := os.Args[1]
+
+	lc := &net.ListenConfig{}
+	lc.SetMultipathTCP(true)
+
+	ln, err := lc.Listen(context.Background(), "tcp", addr)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer ln.Close()
+
+	for {
+		conn, err := ln.Accept()
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		tcp, ok := conn.(*net.TCPConn)
+		if !ok {
+			log.Fatal("struct is not a TCPConn")
+		}
+
+		/* This API is still under discussion: https://go.dev/issue/59166
+		mptcp, err := tcp.MultipathTCP()
+		if err != nil {
+			log.Fatal(err)
+		}
+		*/mptcp := tcp != nil
+
+		log.Printf("connection from %s mptcp %t", addr, mptcp)
+
+		conn.Close()
+	}
+}