package netProgram

import (
	"log"
	"net"
	"os"
)

func UDPServerBasic() {
	// 1.解析地址
	laddr, err := net.ResolveUDPAddr("udp", ":9876")
	if err != nil {
		log.Fatalln(err)
	}

	// 2.监听
	udpConn, err := net.ListenUDP("udp", laddr)
	if err != nil {
		log.Fatalln(err)
	}
	log.Printf("%s server is listening on %s\n", "UDP", udpConn.LocalAddr().String())
	defer udpConn.Close()

	// 3.读
	buf := make([]byte, 1024)
	rn, raddr, err := udpConn.ReadFromUDP(buf)
	if err != nil {
		log.Fatalln(err)
	}
	log.Printf("received %s from %s\n", string(buf[:rn]), raddr.String())

	// 4.写
	data := []byte("received:" + string(buf[:rn]))
	wn, err := udpConn.WriteToUDP(data, raddr)
	if err != nil {
		log.Fatalln(err)
	}
	log.Printf("send %s(%d) to %s\n", string(data), wn, raddr.String())
}

func UDPServerConnect() {
	// 1.解析地址
	laddr, err := net.ResolveUDPAddr("udp", ":9876")
	if err != nil {
		log.Fatalln(err)
	}

	// 2.监听
	udpConn, err := net.ListenUDP("udp", laddr)
	if err != nil {
		log.Fatalln(err)
	}
	log.Printf("%s server is listening on %s\n", "UDP", udpConn.LocalAddr().String())
	defer udpConn.Close()

	// 测试输出远程地址
	log.Println(udpConn.RemoteAddr())

	// 3.读
	buf := make([]byte, 1024)
	rn, raddr, err := udpConn.ReadFromUDP(buf)
	//rn, err := udpConn.Read(buf)
	if err != nil {
		log.Fatalln(err)
	}
	log.Printf("received %s from %s\n", string(buf[:rn]), raddr.String())

	// 测试输出远程地址
	log.Println(udpConn.RemoteAddr())

	// 4.写
	data := []byte("received:" + string(buf[:rn]))
	wn, err := udpConn.WriteToUDP(data, raddr)
	//wn, err := udpConn.Write(data)
	if err != nil {
		log.Fatalln(err)
	}
	log.Printf("send %s(%d) to %s\n", string(data), wn, raddr.String())

	// 测试输出远程地址
	log.Println(udpConn.RemoteAddr())
}

func UDPServerPeer() {
	// 1.解析地址
	laddr, err := net.ResolveUDPAddr("udp", "127.0.0.1:9876")
	if err != nil {
		log.Fatalln(err)
	}

	// 2.监听
	udpConn, err := net.ListenUDP("udp", laddr)
	if err != nil {
		log.Fatalln(err)
	}
	log.Printf("%s server is listening on %s\n", "UDP", udpConn.LocalAddr().String())
	defer udpConn.Close()

	// 远程地址
	raddr, err := net.ResolveUDPAddr("udp", "127.0.0.1:6789")
	if err != nil {
		log.Fatalln(err)
	}

	// 3.读
	buf := make([]byte, 1024)
	rn, raddr, err := udpConn.ReadFromUDP(buf)
	if err != nil {
		log.Fatalln(err)
	}
	log.Printf("received %s from %s\n", string(buf[:rn]), raddr.String())

	// 4.写
	data := []byte("received:" + string(buf[:rn]))
	wn, err := udpConn.WriteToUDP(data, raddr)
	if err != nil {
		log.Fatalln(err)
	}
	log.Printf("send %s(%d) to %s\n", string(data), wn, raddr.String())

}

// 多播接收端
func UDPReceiverMulticast() {
	// 1.多播监听地址
	address := "224.1.1.2:6789"
	gaddr, err := net.ResolveUDPAddr("udp", address)
	if err != nil {
		log.Fatalln(err)
	}

	// 2.多播监听
	udpConn, err := net.ListenMulticastUDP("udp", nil, gaddr)
	if err != nil {
		log.Fatalln(err)
	}

	// 3.接受数据
	// 循环接收
	buf := make([]byte, 1024)
	for {
		rn, raddr, err := udpConn.ReadFromUDP(buf)
		if err != nil {
			log.Println(err)
		}
		log.Printf("received \"%s\" from %s\n", string(buf[:rn]), raddr.String())
	}

}

// 广播接收端
func UDPReceiverBroadcast() {
	// 1.广播监听地址
	laddr, err := net.ResolveUDPAddr("udp", ":6789")
	if err != nil {
		log.Fatalln(err)
	}

	// 2.广播监听
	udpConn, err := net.ListenUDP("udp", laddr)
	if err != nil {
		log.Fatalln(err)
	}
	defer udpConn.Close()
	log.Printf("%s server is listening on %s\n", "UDP", udpConn.LocalAddr().String())

	// 3.接收数据
	// 4.处理数据
	buf := make([]byte, 1024)
	for {
		rn, raddr, err := udpConn.ReadFromUDP(buf)
		if err != nil {
			log.Println(err)
		}
		log.Printf("received \"%s\" from %s\n", string(buf[:rn]), raddr.String())
	}
}

// UDP文件传输
func UDPFileServer() {
	// 1.建立UDP连接
	laddress := ":5678"
	laddr, err := net.ResolveUDPAddr("udp", laddress)
	if err != nil {
		log.Fatalln(err)
	}
	udpConn, err := net.ListenUDP("udp", laddr)
	if err != nil {
		log.Fatalln(err)
	}
	defer udpConn.Close()
	log.Printf("%s server is listening on %s\n", "UDP", udpConn.LocalAddr().String())

	// 2.接收文件名，并确认
	buf := make([]byte, 4*1024)
	rn, raddr, err := udpConn.ReadFromUDP(buf)
	if err != nil {
		log.Fatalln(err)
	}
	filename := string(buf[:rn])
	if _, err := udpConn.WriteToUDP([]byte("filename ok"), raddr); err != nil {
		log.Fatalln(err)
	}

	// 3.接收文件内容，并写入文件
	// 打开文件（创建）
	file, err := os.Create(filename)
	if err != nil {
		log.Fatalln(err)
	}
	defer file.Close()

	// 网络读取
	i := 0
	for {
		// 一次读取
		rn, _, err := udpConn.ReadFromUDP(buf)
		if err != nil {
			log.Fatalln(err)
		}

		// 写入文件
		if _, err := file.Write(buf[:rn]); err != nil {
			log.Fatalln(err)
		}
		i++
		log.Println("file write some content", i)
	}
}