add example tcp server & proxy

examples/tcp/tcp-proxy.go

@@ -0,0 +1,88 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"net"
+	"os"
+	"strconv"
+	"sync"
+)
+
+func main() {
+	if len(os.Args) < 3 {
+		log.Fatalf("requires two arguments; usage: tcp1 <target-port> <source-port>")
+	}
+	sourcePort, err := strconv.Atoi(os.Args[2])
+	if err != nil {
+		log.Fatalf("Failed to parse tcp source port string \"%v\" to int: %v", sourcePort, err)
+	}
+	targetPort, err := strconv.Atoi(os.Args[1])
+	if err != nil {
+		log.Fatalf("Failed to parse tcp target port string \"%v\" to int: %v", targetPort, err)
+	}
+	listener, err := net.Listen("tcp", fmt.Sprintf(":%d", sourcePort))
+	if err != nil {
+		log.Fatalf("Failed to start TCP listener on port %d: %v", sourcePort, err)
+	}
+	defer listener.Close()
+	log.Printf("TCP proxy started: Listening on port %d and forwarding to port %d", sourcePort, targetPort)
+
+	for {
+		conn, err := listener.Accept()
+		if err != nil {
+			log.Printf("Failed to accept connection: %v", err)
+			continue
+		}
+
+		go handleConnection(conn, targetPort)
+	}
+}
+
+func handleConnection(conn net.Conn, targetPort int) {
+	defer conn.Close()
+
+	targetAddr := fmt.Sprintf("localhost:%d", targetPort)
+	target, err := net.Dial("tcp", targetAddr)
+	if err != nil {
+		log.Printf("Failed to dial target server %s: %v", targetAddr, err)
+		return
+	}
+	defer target.Close()
+
+	var wg sync.WaitGroup
+	wg.Add(2)
+
+	// Copy from client to target
+	go func() {
+		_, err := io.Copy(target, conn)
+		if err != nil && !isClosedConnErr(err) {
+			log.Printf("Error copying from client to target: %v", err)
+		}
+		target.Close() // Close target side after copy
+		wg.Done()
+	}()
+
+	// Copy from target to client
+	go func() {
+		_, err := io.Copy(conn, target)
+		if err != nil && !isClosedConnErr(err) {
+			log.Printf("Error copying from target to client: %v", err)
+		}
+		conn.Close() // Close client side after copy
+		wg.Done()
+	}()
+
+	// Wait for both copies to finish
+	wg.Wait()
+}
+
+// isClosedConnErr checks if the error indicates a closed connection.
+func isClosedConnErr(err error) bool {
+	if err == io.EOF {
+		return true
+	}
+	netErr, ok := err.(net.Error)
+	return ok && netErr.Timeout() // Check for timeout error indicating closed connection
+}

examples/tcp/tcp.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"fmt"
+	"net"
+	"os"
+)
+
+func main() {
+	// Start a TCP server listening on port 8000
+	listener, err := net.Listen("tcp", os.Args[1]) //":8000")
+	if err != nil {
+		fmt.Printf("Failed to start server: %v\n", err)
+		return
+	}
+	defer listener.Close()
+	fmt.Println("TCP server started on port " + os.Args[1])
+
+	// Accept and handle incoming connections
+	for {
+		conn, err := listener.Accept()
+		if err != nil {
+			fmt.Printf("Failed to accept connection: %v\n", err)
+			continue
+		}
+		go handleConnection(conn)
+	}
+}
+
+func handleConnection(conn net.Conn) {
+	defer conn.Close()
+
+	// Send a greeting message to the client
+	message := "Hello, World!\n"
+	_, err := conn.Write([]byte(message))
+	if err != nil {
+		fmt.Printf("Error writing response: %v\n", err)
+		return
+	}
+}