server.go

package main

import (
	"io"
	"log"
	"net"
	"time"
)

const (
	// The port to server the
	PORT = ":8082"
)

func main() {

	// Resolves the address of the server port and listens
	addr, err := net.ResolveTCPAddr("tcp", "35.2.213.76"+PORT)
	checkErr(err)
	listener, err := net.ListenTCP("tcp", addr)
	checkErr(err)

	log.Println("Server started.")

	// Indefinitely handle connections
	for {
		newConn, err := listener.AcceptTCP()
		checkErr(err)

		logClientJoined(newConn)
		checkErr(err)

		// Handle connection in a new goroutine
		go handleConn(newConn)
	}
}

// REQUIRES: conn is a pointer to a valid, open TCP connection
// MODIFIES: conn
// EFFECTS:	 Writes a sample message to the connection.
func handleConn(conn *net.TCPConn) {

	for {
		connIsClosed(conn)
		sampleMessage := []byte("Hello!\n")
		_, err := conn.Write(sampleMessage)
		checkErr(err)
		time.Sleep(1000 * time.Millisecond)
	}
}

// REQUIRES: conn is a pointer to a valid, open TCP connection
// EFFECTS:  Logs the event where a client joins.
func logClientJoined(conn *net.TCPConn) {
	log.Println("server.go: Client joined from %s", conn.RemoteAddr())
}

// EFFECTS:	 Handles any non-nil errors by printing them.
func checkErr(err error) {
	if err != nil {
		log.Println("Error: server.go: %s", err.Error())
	}
}

func connIsClosed(c *net.TCPConn) {
	c.SetReadDeadline(time.Now())
	var one []byte
	if _, err := c.Read(one); err == io.EOF {
		log.Println("Client disconnect: %s", c.RemoteAddr())
		c.Close()
		c = nil
	} else {
		var zero time.Time
		c.SetReadDeadline(zero)
	}
}