简介
Go(Golang)中的网络编程具有易用性、强大性和乐趣。本指南深入探讨了网络编程的复杂性,涵盖了协议、TCP/UDP 套接字、并发等方面的内容,并附有详细的注释。
关键概念
1. 网络协议
• TCP(传输控制协议):确保可靠的数据传输。
• UDP(用户数据报协议):更快,但不保证数据传递。
2. 套接字
• TCP 套接字:用于面向连接的通信。
• UDP 套接字:用于无连接通信。
3. 并发
• Goroutines(协程):允许在代码中实现并行处理。
• Channels(通道):用于协程之间的通信。
示例
示例 1:TCP 服务器和客户端
TCP 服务器和客户端示例演示了TCP通信的基础。
服务器
package main
import (
"net"
"fmt"
)
func main() {
// Listen on TCP port 8080 on all available unicast and
// any unicast IP addresses.
listen, err := net.Listen("tcp", ":8080")
if err != nil {
fmt.Println(err)
return
}
defer listen.Close()
// 堆代码 duidaima.com
// Infinite loop to handle incoming connections
for {
conn, err := listen.Accept()
if err != nil {
fmt.Println(err)
continue
}
// Launch a new goroutine to handle the connection
go handleConnection(conn)
}
}
func handleConnection(conn net.Conn) {
defer conn.Close()
buffer := make([]byte, 1024)
// Read the incoming connection into the buffer.
_, err := conn.Read(buffer)
if err != nil {
fmt.Println(err)
return
}
// Send a response back to the client.
conn.Write([]byte("Received: " + string(buffer)))
}
客户端
package main
import (
"net"
"fmt"
)
func main() {
// Connect to the server at localhost on port 8080.
conn, err := net.Dial("tcp", "localhost:8080")
if err != nil {
fmt.Println(err)
return
}
defer conn.Close()
// Send a message to the server.
conn.Write([]byte("Hello, server!"))
buffer := make([]byte, 1024)
// Read the response from the server.
conn.Read(buffer)
fmt.Println(string(buffer))
}
服务器在端口8080上等待连接,读取传入的消息并发送响应。客户端连接到服务器,发送消息并打印服务器的响应。
示例 2:UDP 服务器和客户端
与TCP不同,UDP是无连接的。以下是UDP服务器和客户端的实现。
服务器
package main
import (
"net"
"fmt"
)
func main() {
// Listen for incoming UDP packets on port 8080.
conn, err := net.ListenPacket("udp", ":8080")
if err != nil {
fmt.Println(err)
return
}
defer conn.Close()
buffer := make([]byte, 1024)
// Read the incoming packet data into the buffer.
n, addr, err := conn.ReadFrom(buffer)
if err != nil {
fmt.Println(err)
return
}
fmt.Println("Received: ", string(buffer[:n]))
// Write a response to the client's address.
conn.WriteTo([]byte("Message received!"), addr)
}
客户端
package main
import (
"net"
"fmt"
)
func main() {
// Resolve the server's address.
addr, err := net.ResolveUDPAddr("udp", "localhost:8080")
if err != nil {
fmt.Println(err)
return
}
// Dial a connection to the resolved address.
conn, err := net.DialUDP("udp", nil, addr)
if err != nil {
fmt.Println(err)
return
}
defer conn.Close()
// Write a message to the server.
conn.Write([]byte("Hello, server!"))
buffer := make([]byte, 1024)
// Read the response from the server.
conn.Read(buffer)
fmt.Println(string(buffer))
}
服务器从任何客户端读取消息并发送响应。客户端发送消息并等待响应。
示例 3:并发 TCP 服务器
并发允许同时处理多个客户端。
package main
import (
"net"
"fmt"
)
func main() {
// Listen on TCP port 8080.
listener, err := net.Listen("tcp", ":8080")
if err != nil {
fmt.Println(err)
return
}
defer listener.Close()
for {
// Accept a connection.
conn, err := listener.Accept()
if err != nil {
fmt.Println(err)
continue
}
// Handle the connection in a new goroutine.
go handleConnection(conn)
}
}
func handleConnection(conn net.Conn) {
defer conn.Close()
buffer := make([]byte, 1024)
// Read the incoming connection.
conn.Read(buffer)
fmt.Println("Received:", string(buffer))
// Respond to the client.
conn.Write([]byte("Message received!"))
}
通过为每个连接使用新的 goroutine,多个客户端可以同时连接。
示例 4:带有 Gorilla Mux 的 HTTP 服务器
Gorilla Mux 库简化了 HTTP 请求路由。
package main
import (
"fmt"
"github.com/gorilla/mux"
"net/http"
)
func main() {
// Create a new router.
r := mux.NewRouter()
// Register a handler function for the root path.
r.HandleFunc("/", homeHandler)
http.ListenAndServe(":8080", r)
}
func homeHandler(w http.ResponseWriter, r *http.Request) {
// Respond with a welcome message.
fmt.Fprint(w, "Welcome to Home!")
}
这段代码设置了一个 HTTP 服务器,并为根路径定义了一个处理函数。
示例 5:HTTPS 服务器
实现 HTTPS 服务器可以确保安全通信。
package main
import (
"net/http"
"log"
)
func main() {
http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
// Respond with a message.
w.Write([]byte("Hello, this is an HTTPS server!"))
})
// Use the cert.pem and key.pem files to secure the server.
log.Fatal(http.ListenAndServeTLS(":8080", "cert.pem", "key.pem", nil))
}
服务器使用 TLS(传输层安全性)来加密通信。
示例 6:自定义 TCP 协议
可以使用自定义的 TCP 协议进行专门的通信。
package main
import (
"net"
"strings"
)
func main() {
// Listen on TCP port 8080.
listener, err := net.Listen("tcp", ":8080")
if err != nil {
panic(err)
}
defer listener.Close()
for {
// Accept a connection.
conn, err := listener.Accept()
if err != nil {
panic(err)
}
// Handle the connection in a new goroutine.
go handleConnection(conn)
}
}
func handleConnection(conn net.Conn) {
defer conn.Close()
buffer := make([]byte, 1024)
// Read the incoming connection.
conn.Read(buffer)
// Process custom protocol command.
cmd := strings.TrimSpace(string(buffer))
if cmd == "TIME" {
conn.Write([]byte("The current time is: " + time.Now().String()))
} else {
conn.Write([]byte("Unknown command"))
}
}
这段代码实现了一个简单的自定义协议,当客户端发送命令“TIME”时,它会回复当前时间。
示例 7:使用 Gorilla WebSocket 进行 WebSockets
WebSockets 提供了通过单一连接的实时全双工通信。
package main
import (
"github.com/gorilla/websocket"
"net/http"
)
var upgrader = websocket.Upgrader{
ReadBufferSize: 1024,
WriteBufferSize: 1024,
}
func handler(w http.ResponseWriter, r *http.Request) {
conn, err := upgrader.Upgrade(w, r, nil)
if err != nil {
http.Error(w, "Could not open websocket connection", http.StatusBadRequest)
return
}
defer conn.Close()
for {
messageType, p, err := conn.ReadMessage()
if err != nil {
return
}
// Echo the message back to the client.
conn.WriteMessage(messageType, p)
}
}
func main() {
http.HandleFunc("/", handler)
http.ListenAndServe(":8080", nil)
}
WebSocket 服务器会将消息回传给客户端。
示例 8:连接超时
可以使用 context 包来管理连接超时。
package main
import (
"context"
"fmt"
"net"
"time"
)
func main() {
// Create a context with a timeout of 2 seconds
ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
defer cancel()
// Dialer using the context
dialer := net.Dialer{}
conn, err := dialer.DialContext(ctx, "tcp", "localhost:8080")
if err != nil {
panic(err)
}
buffer := make([]byte, 1024)
_, err = conn.Read(buffer)
if err == nil {
fmt.Println("Received:", string(buffer))
} else {
fmt.Println("Connection error:", err)
}
}
这段代码为从连接读取数据设置了两秒的截止时间。
示例 9:使用 golang.org/x/time/rate 进行速率限制
速率限制控制请求的速率。
package main
import (
"golang.org/x/time/rate"
"net/http"
"time"
)
// Define a rate limiter allowing two requests per second with a burst capacity of five.
var limiter = rate.NewLimiter(2, 5)
func handler(w http.ResponseWriter, r *http.Request) {
// Check if request is allowed by the rate limiter.
if !limiter.Allow() {
http.Error(w, "Too Many Requests", http.StatusTooManyRequests)
return
}
w.Write([]byte("Welcome!"))
}
func main() {
http.HandleFunc("/", handler)
http.ListenAndServe(":8080", nil)
}
此示例使用速率限制器,将请求速率限制为每秒两个请求,突发容量为五个。