Add simple proxy.

cmd/sprox/main.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"flag"
+	"io"
+	"log"
+	"net"
+
+	"github.com/kisom/goutils/die"
+)
+
+func proxy(conn net.Conn, inside string) error {
+	proxyConn, err := net.Dial("tcp", inside)
+	if err != nil {
+		return err
+	}
+
+	defer proxyConn.Close()
+	defer conn.Close()
+
+	go func() {
+		io.Copy(conn, proxyConn)
+	}()
+	_, err = io.Copy(proxyConn, conn)
+	return err
+}
+
+func main() {
+	var outside, inside string
+	flag.StringVar(&outside, "f", "8080", "outside port")
+	flag.StringVar(&inside, "p", "4000", "inside port")
+	flag.Parse()
+
+	l, err := net.Listen("tcp", "0.0.0.0:"+outside)
+	die.If(err)
+
+	for {
+		conn, err := l.Accept()
+		if err != nil {
+			log.Println(err)
+			continue
+		}
+
+		go proxy(conn, "127.0.0.1:"+inside)
+	}
+}