client

package main

import (
	"bufio"
	"fmt"
	"net"
	"os"
)

func main() {

	// connect to this socket
	conn, _ := net.Dial("tcp", "127.0.0.1:8080")
	for {
		// read in input from stdin
		reader := bufio.NewReader(os.Stdin)
		fmt.Print("Text to send: ")
		text, _ := reader.ReadString('\n')
		// send to socket
		fmt.Fprintf(conn, text+"\n")
		// listen for reply
		message, _ := bufio.NewReader(conn).ReadString('\n')
		fmt.Print(message)
	}

}






server

package main

import (
	"bufio"
	"encoding/json"
	"log"
	"net"
	"os"
	"strconv"
)

type Configuration struct {
	Port      int
	MaxLength int
	MODE      string
	SHIFT     int
}

var mode string
var shift int
var indx int
var maxLength int

const lowerCaseAlphabet = "abcdefghijklmnopqrstuvwxyz"
const upperCaseAlphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"

func main() {

	//filename is the path to the json config file
	config := Configuration{}
	file, err := os.Open("config.json")
	if err != nil {
		log.Fatal(err)
	}
	decoder := json.NewDecoder(file)
	err = decoder.Decode(&config)
	if err != nil {
		log.Fatal(err)
	}

	listener, err := net.Listen("tcp", "127.0.0.1:"+strconv.Itoa(config.Port))
	if err != nil {
		log.Fatal("tcp server listener error:", err)
	}

	mode = config.MODE
	shift = config.SHIFT
	maxLength = config.MaxLength

	for {
		conn, err := listener.Accept()
		if err != nil {
			log.Fatal("tcp server accept error", err)
		}
		clientAddr := conn.RemoteAddr().String()
		log.Println("Clientul " + clientAddr + " s-a conectat.")
		go handleConnection(conn)
	}
}
func mod(x, d int) int {
	x = x % d
	if x >= 0 {
		return x
	}
	if d < 0 {
		return x - d
	}
	return x + d
}
func handleConnection(conn net.Conn) {
	bufferBytes, err := bufio.NewReader(conn).ReadBytes('\n')
	clientAddr := conn.RemoteAddr().String()
	if err != nil {
		log.Println("Clientul " + clientAddr + " a iesit.")
		conn.Close()
		return
	}
	message := string(bufferBytes)
	log.Println("Clientul " + clientAddr + " a trimis: " + message)
	if len(message)-2 > maxLength {
		log.Println("Textul depaseste limita de caractere")
		conn.Write([]byte("Textul depaseste limita de caractere\n"))
	} else {
		//response := fmt.Sprintf(message + " from " + clientAddr + "\n")
		rotatedText := []byte(message)
		if mode == "LEFT" {
			indx = -1
		} else {
			indx = 1
		}
		for index, byteValue := range rotatedText {
			if byteValue >= 'a' && byteValue <= 'z' {
				rotatedText[index] = lowerCaseAlphabet[mod(int(byteValue-'a')+indx*shift, 26)]
			} else if byteValue >= 'A' && byteValue <= 'Z' {
				rotatedText[index] = upperCaseAlphabet[mod(int(byteValue-'A')+indx*shift, 26)]
			}
		}

		log.Println("Textul trimis la " + clientAddr + "este: " + string(rotatedText))

		conn.Write([]byte("Textul codat: " + string(rotatedText)))

	}

	handleConnection(conn)
}