package main
import (
	"fmt"
	"net"
)
func main() {
	// 創建監聽
	socket, err := net.ListenUDP("udp4", &net.UDPAddr{
		IP:   net.IPv4(0, 0, 0, 0),
		Port: 8080,
	})
	if err != nil {
		fmt.Println("監聽失敗!", err)
		return
	}
	defer socket.Close()
	for {
		// 讀取客戶端傳來的數據
		data := make([]byte, 4096)
		read, remoteAddr, err := socket.ReadFromUDP(data)
		if err != nil {
			fmt.Println("讀取數據失敗!", err)
			continue
		}
		fmt.Println(read, remoteAddr)
		fmt.Printf("%s\n\n", data)
		//發送數據,告訴客戶端已收到
		senddata := []byte("hello client!")
		_, err = socket.WriteToUDP(senddata, remoteAddr)
		if err != nil {
			return
			fmt.Println("發送數據失敗!", err)
		}
	}
}

package main
import (
	"fmt"
	"net"
)
func main() {
	// 創建連接
	socket, err := net.DialUDP("udp4", nil, &net.UDPAddr{
		IP:   net.IPv4(0, 0, 0, 0),
		Port: 8080,
	})
	if err != nil {
		fmt.Println("連接失敗!", err)
		return
	}
	defer socket.Close()
	// 發送給服務端數據
	senddata := []byte("hello server!")
	_, err = socket.Write(senddata)
	if err != nil {
		fmt.Println("發送數據失敗!", err)
		return
	}
	// 接收客戶端的數據
	data := make([]byte, 4096)
	read, remoteAddr, err := socket.ReadFromUDP(data)
	if err != nil {
		fmt.Println("讀取數據失敗!", err)
		return
	}
	fmt.Println(read, remoteAddr)
	fmt.Printf("%s\n", data)
}

package main
import (
	"fmt"
	"net"
)
func main() {
	//監聽
	listener, err := net.Listen("tcp", "127.0.0.1:8000")
	if err != nil {
		fmt.Println("err = ", err)
		return
	}
	defer listener.Close()
	//阻塞等待用戶鏈接
	conn, err := listener.Accept()
	if err != nil {
		fmt.Println("err = ", err)
		return
	}
	//接收用戶的請求
	buf := make([]byte, 1024) //1024大小的緩沖區
	n, err1 := conn.Read(buf)
	if err1 != nil {
		fmt.Println("err1 = ", err1)
		return
	}
	fmt.Println("buf = ", string(buf[:n]))
	defer conn.Close() //關閉當前用戶鏈接
}

package main
import (
	"fmt"
	"net"
)
func main() {
	//主動連接服務器
	conn, err := net.Dial("tcp", "127.0.0.1:8000")
	if err != nil {
		fmt.Println("err = ", err)
		return
	}
	defer conn.Close()
	//發送數據
	conn.Write([]byte("are u ok?"))
}

package main
import (
	"fmt"
	"net"
	"strings"
)
//處理用戶請求
func HandleConn(conn net.Conn) {
	//函數調用完畢，自動關閉conn
	defer conn.Close()
	//獲取客戶端的網絡地址信息
	addr := conn.RemoteAddr().String()
	fmt.Println(addr, " conncet sucessful")
	buf := make([]byte, 2048)
	for {
		//讀取用戶數據
		n, err := conn.Read(buf)
		if err != nil {
			fmt.Println("err = ", err)
			return
		}
		fmt.Printf("[%s]: %s\n", addr, string(buf[:n]))
		fmt.Println("len = ", len(string(buf[:n])))
		//if "exit" == string(buf[:n-1]) { //nc測試
		if "exit" == string(buf[:n-2]) { //自己寫的客戶端測試, 發送時，多了2個字符, "\r\n"
			fmt.Println(addr, " exit")
			return
		}
		//把數據轉換為大寫，再給用戶發送
		conn.Write([]byte(strings.ToUpper(string(buf[:n]))))
	}

}
func main() {
	//監聽
	listener, err := net.Listen("tcp", "127.0.0.1:8000")
	if err != nil {
		fmt.Println("err = ", err)
		return
	}
	defer listener.Close()
	//接收多個用戶
	for {
		conn, err := listener.Accept()
		if err != nil {
			fmt.Println("err = ", err)
			return
		}
		//處理用戶請求, 新建一個協程
		go HandleConn(conn)
	}
}

package main
import (
	"fmt"
	"net"
	"os"
)
func main() {
	//主動連接服務器
	conn, err := net.Dial("tcp", "127.0.0.1:8000")
	if err != nil {
		fmt.Println("net.Dial err = ", err)
		return
	}
	//main調用完畢，關閉連接
	defer conn.Close()
	go func() {
		//從鍵盤輸入內容，給服務器發送內容
		str := make([]byte, 1024)
		for {
			n, err := os.Stdin.Read(str) //從鍵盤讀取內容， 放在str
			if err != nil {
				fmt.Println("os.Stdin. err = ", err)
				return
			}
			//把輸入的內容給服務器發送
			conn.Write(str[:n])
		}
	}()
	//接收服務器回復的數據
	//切片緩沖
	buf := make([]byte, 1024)
	for {
		n, err := conn.Read(buf) //接收服務器的請求
		if err != nil {
			fmt.Println("conn.Read err = ", err)
			return
		}
		fmt.Println(string(buf[:n])) //打印接收到的內容, 轉換為字符串再打印
	}
}