var msg []byte // msg 是一個(gè)nil切片，長(zhǎng)度和容量都為0
n, err := c.Read(msg)

// 分配一個(gè)1024字節(jié)的緩沖區(qū)
msg := make([]byte, 1024)
n, err := c.Read(msg)

if err == io.EOF {
    fmt.Printf("SERVER: Client %s disconnected (EOF).\n", c.RemoteAddr())
    return // 客戶端已關(guān)閉連接，此goroutine可以退出
} else if err != nil {
    fmt.Printf("SERVER: Error reading from %s: %v\n", c.RemoteAddr(), err)
    return // 其他讀取錯(cuò)誤，也退出
}

// 只將實(shí)際讀取的n個(gè)字節(jié)寫回
_, err = c.Write(msg[:n])

package main

import (
    "fmt"
    "io"
    "net"
    "sync"
)

// echo_srv 處理單個(gè)客戶端連接
func echo_srv(c net.Conn, wg *sync.WaitGroup) {
    defer c.Close()    // 確保連接在函數(shù)結(jié)束時(shí)關(guān)閉
    defer wg.Done()    // 確保WaitGroup計(jì)數(shù)器在goroutine結(jié)束時(shí)遞減

    fmt.Printf("SERVER: Accepted connection from %s\n", c.RemoteAddr())

    // 循環(huán)讀取和回寫數(shù)據(jù)
    for {
        // 1. 分配一個(gè)緩沖區(qū)來(lái)接收數(shù)據(jù)
        msg := make([]byte, 1024) // 使用1KB緩沖區(qū)

        // 2. 從連接中讀取數(shù)據(jù)
        n, err := c.Read(msg)
        if err == io.EOF {
            // 客戶端已關(guān)閉連接
            fmt.Printf("SERVER: Client %s disconnected (EOF).\n", c.RemoteAddr())
            return // 退出goroutine
        } else if err != nil {
            // 其他讀取錯(cuò)誤
            fmt.Printf("SERVER: Error reading from %s: %v\n", c.RemoteAddr(), err)
            return // 退出goroutine
        }

        // 打印接收到的字節(jié)數(shù)和內(nèi)容
        fmt.Printf("SERVER: Received %v bytes from %s: %s\n", n, c.RemoteAddr(), string(msg[:n]))

        // 3. 將接收到的數(shù)據(jù)（只回寫實(shí)際讀取的n個(gè)字節(jié)）寫回客戶端
        _, err = c.Write(msg[:n]) // 忽略寫入的字節(jié)數(shù)，因?yàn)槲覀兤谕繉懭?        if err != nil {
            fmt.Printf("SERVER: Error writing to %s: %v\n", c.RemoteAddr(), err)
            return // 退出goroutine
        }
        fmt.Printf("SERVER: Sent %v bytes back to %s\n", n, c.RemoteAddr())
    }
}

func main() {
    var wg sync.WaitGroup

    // 監(jiān)聽(tīng)Unix域套接字
    // 注意：實(shí)際應(yīng)用中可能更常用TCP監(jiān)聽(tīng)，例如 "tcp", ":8080"
    socketPath := "./sock_srv"
    ln, err := net.Listen("unix", socketPath)
    if err != nil {
        fmt.Printf("SERVER: Error listening on %s: %v\n", socketPath, err)
        return
    }
    defer ln.Close() // 確保監(jiān)聽(tīng)器在main函數(shù)結(jié)束時(shí)關(guān)閉
    fmt.Printf("SERVER: Listening on %s...\n", socketPath)

    // 循環(huán)接受多個(gè)客戶端連接
    for {
        conn, err := ln.Accept()
        if err != nil {
            fmt.Printf("SERVER: Error accepting connection: %v\n", err)
            // 如果是臨時(shí)錯(cuò)誤，可以考慮繼續(xù)循環(huán)；如果是致命錯(cuò)誤，可能需要退出
            continue
        }

        wg.Add(1) // 每接受一個(gè)連接，WaitGroup計(jì)數(shù)器加1
        go echo_srv(conn, &wg) // 啟動(dòng)一個(gè)goroutine處理連接，并傳遞WaitGroup的指針
    }

    // 對(duì)于一個(gè)持續(xù)運(yùn)行的服務(wù)器，通常不會(huì)在main函數(shù)末尾直接調(diào)用wg.Wait()，
    // 因?yàn)樗鼤?huì)阻塞主goroutine，阻止接受新的連接。
    // 如果服務(wù)器需要優(yōu)雅關(guān)閉并等待所有客戶端goroutine完成，
    // 通常會(huì)在一個(gè)信號(hào)處理函數(shù)中調(diào)用 wg.Wait()。
    // 此處為演示，如果希望main函數(shù)在所有客戶端處理完畢后退出，可以取消注釋以下行：
    // wg.Wait()
    // fmt.Println("SERVER: All client goroutines finished.")
}

package main

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

func main() {
    stdin := bufio.NewReader(os.Stdin)

    // 連接到服務(wù)器
    socketPath := "./sock_srv"
    conn, err := net.Dial("unix", socketPath)
    if err != nil {
        fmt.Printf("CLIENT: Error connecting to %s: %v\n", socketPath, err)
        return
    }
    defer conn.Close()
    fmt.Printf("CLIENT: Connected to %s\n", socketPath)

    for {
        fmt.Print("Enter message to transmit (type 'quit' or 'exit' to close): ")
        msgInput, err := stdin.ReadString('\n')
        if err != nil {
            fmt.Printf("CLIENT: Error reading from stdin: %v\n", err)
            return
        }

        // 移除換行符
        msgInput = strings.TrimSpace(msgInput)

        if strings.ToLower(msgInput) == "quit" || strings.ToLower(msgInput) == "exit" {
            fmt.Println("CLIENT: Disconnecting...")
            return
        }

        // 發(fā)送消息