Go: how to create a TCP client and server

Go, also known as Golang, is an open-source programming language developed by Google. Its simplicity, efficiency and ease of use make it perfect for building network applications such as clients and servers. In this article, well explore how to create a TCP client and server in Go.

What is TCP?

Transmission Control Protocol (TCP) is a connection-oriented, reliable communication protocol used to transfer data over a network. Being a reliable protocol, TCP ensures the delivery of data without errors and in correct order.

Create the TCP Server

Lets start by creating the TCP server that will listen for incoming connections and handle client requests. Here is the code for the TCP server in Go:

package main

import (
	"fmt"
	"net"
)

func handleConnection(conn net.Conn) {
	defer conn.Close()

	// Qui puoi gestire la connessione con il client.
	// Ad esempio, puoi leggere i dati inviati dal client o rispondere alle sue richieste.

	fmt.Println("Nuova connessione accettata:", conn.RemoteAddr().String())

	// Esempio di lettura dei dati inviati dal client
	buffer := make([]byte, 1024)
	n, err := conn.Read(buffer)
	if err != nil {
		fmt.Println("Errore durante la lettura dei dati:", err)
		return
	}
	fmt.Printf("Dati ricevuti: %s\n", buffer[:n])
}

func main() {
	// Avvia il server sulla porta 8080
	listener, err := net.Listen("tcp", ":8080")
	if err != nil {
		fmt.Println("Errore durante l'avvio del server:", err)
		return
	}
	defer listener.Close()

	fmt.Println("Server in ascolto su", listener.Addr())

	for {
		// Accetta una nuova connessione
		conn, err := listener.Accept()
		if err != nil {
			fmt.Println("Errore durante l'accettazione della connessione:", err)
			return
		}

		// Gestisci la connessione in modo asincrono
		go handleConnection(conn)
	}
}

The server creates a socket listening on port 8080 using net.Listen . When a client connects, the connection is accepted using listener.Accept() , and the server will handle the connection asynchronously using the go handleConnection(conn) goroutine.

The handleConnection function is responsible for managing the connection with the client. Currently, it just prints data received from the client, but you can customize it to respond to client requests based on your needs.

Create the TCP Client

Now that we have our server up and running, lets create a TCP client that connects to the server and sends data. Here is the code for the TCP client in Go:

package main

import (
	"fmt"
	"net"
)

func main() {
	// Connetti il client al server
	conn, err := net.Dial("tcp", "localhost:8080")
	if err != nil {
		fmt.Println("Errore durante la connessione al server:", err)
		return
	}
	defer conn.Close()

	// Dati da inviare al server
	data := "Ciao, server! Sono un client."

	// Invia i dati al server
	_, err = conn.Write([]byte(data))
	if err != nil {
		fmt.Println("Errore durante l'invio dei dati:", err)
		return
	}

	fmt.Println("Dati inviati al server:", data)
}

The client connects to the server using net.Dial and specifying the address and port of the server to connect to. After that, it sends the data to the server using conn.Write([]byte(data)) .

Running Server and Client

To run the server, save the server code in a file called server.go and the client code in a file called client.go . Next, open two terminals and navigate to both folders containing the respective client and server files.

In the first terminal, run the server:

go run server.go

In the second terminal, run the client:

go run client.go

You should see server output indicating receiving data from the client and client output indicating sending data to the server.