From 461a032a9af8ad37828be10ad8ee814b222c99a4 Mon Sep 17 00:00:00 2001 From: Shawn Hsu Date: Sat, 18 May 2024 01:47:27 +0800 Subject: [PATCH] (#9) Add TCP/UDP example --- _posts/network/2024-05-07-network-basics.md | 227 +++++++++++++++++++- 1 file changed, 226 insertions(+), 1 deletion(-) diff --git a/_posts/network/2024-05-07-network-basics.md b/_posts/network/2024-05-07-network-basics.md index f56992c612c2..a6dbd2c20a76 100644 --- a/_posts/network/2024-05-07-network-basics.md +++ b/_posts/network/2024-05-07-network-basics.md @@ -443,7 +443,232 @@ record protocol 主要是用於封裝高階 protocol 的資料\ |Used Socket|2|1| # TCP/UDP Golang Example -> to be continued +詳細的程式碼可以參考 [ambersun1234/blog-labs/echo-tcp-udp](https://github.com/ambersun1234/blog-labs/tree/master/echo-tcp-udp) + +## TCP +```go +func tcpHandle(conn net.Conn) { + defer conn.Close() + + scann := bufio.NewScanner(conn) + for scann.Scan() { + input := scann.Text() + + logger.Println("Receive: ", input) + if _, err := conn.Write([]byte(fmt.Sprintf("%s\n", input))); err != nil { + logger.Fatalln(err) + } + } +} + +func tcpServer() { + li, err := net.Listen("tcp", fmt.Sprintf(":%d", tcpPort)) + if err != nil { + logger.Fatalln(err) + } + defer li.Close() + logger.Printf("Listening on: localhost:%v\n", tcpPort) + + for { + conn, err := li.Accept() + if err != nil { + logger.Fatalln(err) + } + if err := conn.SetDeadline(time.Time{}); err != nil { + logger.Fatalln(err) + } + + go tcpHandle(conn) + } +} + +func tcpClient() { + host := os.Getenv("HOST") + conn, err := net.Dial("tcp", fmt.Sprintf("%v:%d", host, tcpPort)) + if err != nil { + logger.Fatalln(err) + } + + ticker := time.NewTicker(2 * time.Second) + for { + <-ticker.C + + // send data + msg := "Hello World!" + logger.Println("Send: ", msg) + if _, err := conn.Write([]byte(fmt.Sprintf("%s\n", msg))); err != nil { + logger.Fatalln(err) + } + + // receive data + data, err := bufio.NewReader(conn).ReadString('\n') + if err != nil { + logger.Fatalln(err) + } + logger.Printf("Server ACK with: '%v'\n", string(data)) + } +} +``` +基本上需要注意的點是 +1. TCP 是以換行為分隔符號, 所以你送資料的時候記得加 `\n` + +其他就相對單純\ +用一個 for-loop 持續監聽連線\ +當新的連線進來的時候，就開啟 goroutine 來處理它(line 32)\ +這也是為什麼上面我們說 [TCP](#tcp---transmission-control-protocol) 需要兩個 sockets + +## UDP Unicast +```go +func udpUnicastHandle(conn *net.UDPConn) { + buf := make([]byte, 1024) + + for { + n, adr, err := conn.ReadFromUDP(buf) + if err != nil { + logger.Fatalln(err) + } + + data := string(buf[:n]) + logger.Println("Receive: ", data) + if _, err := conn.WriteToUDP([]byte(fmt.Sprintf("%v\n", data)), adr); err != nil { + logger.Fatalln(err) + } + } +} + +func udpUnicastServer() { + address := net.UDPAddr{ + Port: udpUnicastPort, + IP: net.ParseIP("0.0.0.0"), + } + li, err := net.ListenUDP("udp", &address) + if err != nil { + logger.Fatalln(err) + } + logger.Printf("Listening on: localhost:%v\n", udpUnicastPort) + + udpUnicastHandle(li) +} + +func udpUnicastClient() { + host := os.Getenv("HOST") + conn, err := net.Dial("udp", fmt.Sprintf("%v:%d", host, udpUnicastPort)) + if err != nil { + logger.Fatalln(err) + } + + ticker := time.NewTicker(2 * time.Second) + for { + <-ticker.C + + // send data + msg := "Hello World!" + logger.Println("Send: ", msg) + if _, err := conn.Write([]byte(msg)); err != nil { + logger.Fatalln(err) + } + + // receive data + data, err := bufio.NewReader(conn).ReadString('\n') + if err != nil { + logger.Fatalln(err) + } + logger.Printf("Server ACK with: '%v'\n", string(data)) + } +} +``` + +跟 [TCP](#tcp) 的實作可以說是一模一樣\ +差在它不會預先建立連線\ +然後一些 function 改成使用 UDP 版本的這樣而已 + +## UDP Multicast +```go +func udpMulticastHandle(conn *net.UDPConn) { + address, err := net.ResolveUDPAddr("udp", fmt.Sprintf("%v:%v", udpMulticastHost, udpMulticastPort)) + if err != nil { + logger.Fatalln(err) + } + buf := make([]byte, 1024) + + for { + n, _, err := conn.ReadFromUDP(buf) + if err != nil { + logger.Fatalln(err) + } + + data := string(buf[:n]) + logger.Println("Receive: ", data) + if _, err := conn.WriteTo([]byte(fmt.Sprintf("%v\n", data)), address); err != nil { + logger.Fatalln(err) + } + } +} + +func udpMulticastServer() { + address, err := net.ResolveUDPAddr("udp", fmt.Sprintf("%v:%v", udpMulticastHost, udpMulticastPort)) + if err != nil { + logger.Fatalln(err) + } + li, err := net.ListenMulticastUDP("udp", nil, address) + if err != nil { + logger.Fatalln(err) + } + logger.Printf("Listening on: localhost:%v\n", udpMulticastPort) + + udpMulticastHandle(li) +} + +func udpMulticastClient() { + address, err := net.ResolveUDPAddr("udp", fmt.Sprintf("%v:%v", udpMulticastHost, udpMulticastPort)) + if err != nil { + logger.Fatalln(err) + } + + conn, err := net.ListenMulticastUDP("udp", nil, address) + if err != nil { + logger.Fatalln(err) + } + + ticker := time.NewTicker(2 * time.Second) + for { + <-ticker.C + + // send data + msg := "Hello World!" + logger.Println("Send: ", msg) + if _, err := conn.WriteTo([]byte(msg), address); err != nil { + logger.Fatalln(err) + } + + // receive data + data, err := bufio.NewReader(conn).ReadString('\n') + if err != nil { + logger.Fatalln(err) + } + logger.Printf("Server ACK with: '%v'\n", string(data)) + } +} +``` + +UDP Multicast 就有意思的多了\ +首先，你必須使用 `ListenMulticastUDP` 這個 function\ +不論 client 或 server\ +注意到不能使用 ListenUDP + +另外一個有趣的點是先前在 [Multicast](#multicast) 提到\ +群播發送訊息的人不會收到自己的訊息\ +根據 [https://pkg.go.dev/net#ListenMulticastUDP](https://pkg.go.dev/net#ListenMulticastUDP) 裡面提到 + +> Note that ListenMulticastUDP will set the IP_MULTICAST_LOOP socket option to 0 under IPPROTO_IP, to disable loopback of multicast packets. + +而你在測試 Multicast 的時候就必須要使用不同的機器\ +才可以正確的讀取到群播的資料\ +並不需要手動撰寫過濾自身訊息的程式(你必須要使用 `ListenMulticastUDP` 這個 function) + +並且，server 寫資料的時候也要注意\ +因為是群播，所以你的 destination 也必須要是 `群播地址`(第 16 行)\ +不要寫成 client address 不然你會讀不到資料 # References + 電腦網際網路(ISBN: 978-986-463-950-2)