Add golang/tcpproxy.go

golang/tcpproxy.go

@@ -0,0 +1,60 @@
+// Example usage:
+// Terminal 1: python -m http.server 8000
+// Terminal 2: go run tcpproxy.go 9000 localhost:8000
+// Terminal 3: curl localhost:9000
+package main
+
+import (
+	"fmt"
+	"io"
+	"net"
+	"os"
+)
+
+func main() {
+	if len(os.Args) != 3 {
+		fmt.Println("Usage: go run tcpproxy.go <listen_port> <target_host:port>")
+		os.Exit(1)
+	}
+	
+	listenPort := os.Args[1]   // port to listen on
+	targetAddr := os.Args[2]   // target server address
+	
+	// create TCP listener on specified port
+	listener, err := net.Listen("tcp", ":"+listenPort)
+	if err != nil {
+		fmt.Printf("Failed to listen on port %s: %v\n", listenPort, err)
+		os.Exit(1)
+	}
+	defer listener.Close()
+	
+	fmt.Printf("TCP proxy listening on port %s, forwarding to %s\n", listenPort, targetAddr)
+	
+	// accept incoming connections
+	for {
+		clientConn, err := listener.Accept()
+		if err != nil {
+			fmt.Printf("Failed to accept connection: %v\n", err)
+			continue
+		}
+		
+		// handle each client connection concurrently
+		go handleConnection(clientConn, targetAddr)
+	}
+}
+
+func handleConnection(clientConn net.Conn, targetAddr string) {
+	defer clientConn.Close() // ensure client connection is closed
+	
+	// connect to target server
+	serverConn, err := net.Dial("tcp", targetAddr)
+	if err != nil {
+		fmt.Printf("Failed to connect to target %s: %v\n", targetAddr, err)
+		return
+	}
+	defer serverConn.Close() // ensure server connection is closed
+	
+	// start bidirectional data copying
+	go io.Copy(serverConn, clientConn) // client -> server
+	io.Copy(clientConn, serverConn)    // server -> client (blocks until done)
+}