Golang - TCP client/server echo 예제 코드

서버 측 코드와,

package main

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

func main() {
    sock, err := net.Listen("tcp", ":18080")
    if err != nil {
        log.Fatalf("Failed to bind address: %v", err)
    }
    
    defer sock.Close()
    
    for {
        conn, err := sock.Accept()
        if err != nil {
            log.Printf("Failed to accept: %v", err)
            continue
        }
        
        go ClientHandler(conn)
    }
}

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

    recvBuf := make([]byte, 4096)

    for {

        readBytes, err := conn.Read(recvBuf)
        if err != nil {
            if err == io.EOF {
                log.Printf("Client closed the socket: %v", conn.RemoteAddr().String())
                return
            }

            log.Printf("Failed to receive data: %v", err)
            return
        }

        if readBytes > 0 {
            data := recvBuf[:readBytes]

            if number, err := strconv.Atoi(strings.Trim(string(data), string('\n'))); err == nil {
                time.Sleep(time.Duration(number) * time.Second)
            }

            conn.Write(data)

            log.Println(string(data))
        } else {
            log.Println("Can you see me?")
        }

    }
}

package main

import (
    "bufio"
    "fmt"
    "io"
    "log"
    "net"
    "os"
    "strconv"
    "strings"
)

func main() {
    socket, err := net.Dial("tcp", "localhost:18080")
    if err != nil {
        log.Fatalf("Failed to connect to server: %v", err)
        return
    }

    defer socket.Close()
    console := bufio.NewReader(os.Stdin)
    recvBuf := make([]byte, 4096)

    for {
        fmt.Print("socket> ")
        text, _ := console.ReadString('\n')

        if number, err := strconv.Atoi(strings.Trim(string(text), string('\n'))); err == nil {
            fmt.Printf("Echo delayed: %v\n", number)
        }

        if text == "quit\n" {
            break
        }
        socket.Write([] byte(text))

        readBytes, err := socket.Read(recvBuf)
        if err != nil {
            if err == io.EOF {
                fmt.Printf("Server closed the socket: %v", socket.RemoteAddr().String())
                return
            }

            fmt.Printf("Failed to receive data: %v", err)
            return
        }

        if readBytes > 0 {
            data := recvBuf[:readBytes]
            fmt.Println(string(data))
        } else {
            fmt.Println("Can you see me?")
        }
    }
}

[서버 측]
2021/09/03 15:39:10 test

2021/09/03 15:39:12 qwer

2021/09/03 15:39:18 5

2021/09/03 15:39:23 Client closed the socket: [::1]:1264



[클라이언트 측]
socket> test
test

socket> qwer
qwer

socket> 5
Echo delayed: 5
5

socket> quit

Debugger finished with the exit code 0