Go TCP客户端即时发送数据：SetNoDelay的实践与服务器端诊断

package main

import (
    "fmt"
    "net"
    "os"
)

func main() {
    addr, err := net.ResolveTCPAddr("tcp", "localhost:5432")
    if err != nil {
        fmt.Println("ResolveTCPAddr fail:", err)
        return
    }

    conn, err := net.DialTCP("tcp", nil, addr)
    if err != nil {
        fmt.Println("Connect fail:", err)
        return
    }
    defer conn.Close()

    // 禁用Nagle算法，期望立即发送数据
    err = conn.SetNoDelay(true)
    if err != nil {
        fmt.Println("SetNoDelay error:", err)
    }

    fmt.Println("Connected to server. Enter messages (empty line to quit):")

    for {
        var message string
        // 从标准输入读取一行
        _, err := fmt.Scanln(&message)
        if err != nil {
            // 忽略 "unexpected newline" 错误，处理其他错误
            if err.Error() != "unexpected newline" {
                fmt.Println("Input finished or error:", err)
                break
            }
        }

        if message == "" {
            fmt.Println("No input, ending connection.")
            break
        }

        // 使用conn.Write发送数据
        _, err = conn.Write([]byte(message + "\n")) // 加上换行符以便服务器端按行读取
        if err != nil {
            fmt.Println("Write error:", err)
            break
        }
        fmt.Println("Sent:", message)
    }
    fmt.Println("Client connection closed.")
}

package main

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

func main() {
    // 监听本地5432端口
    l, err := net.Listen("tcp", "localhost:5432")
    if err != nil {
        log.Fatalf("Failed to listen: %v", err)
    }
    defer l.Close()
    log.Println("Server listening on localhost:5432")

    for {
        // 接受新的客户端连接
        conn, err := l.Accept()
        if err != nil {
            log.Printf("Failed to accept connection: %v", err)
            continue
        }
        log.Printf("Accepted connection from %s", conn.RemoteAddr())

        // 为每个连接启动一个goroutine处理
        go func(c net.Conn) {
            defer c.Close()
            defer log.Printf("Connection from %s closed", c.RemoteAddr())

            // 将客户端发送的所有数据直接复制到标准输出
            // io.Copy会阻塞直到EOF或错误
            _, err := io.Copy(os.Stdout, c)
            if err != nil && err != io.EOF {
                log.Printf("Error during io.Copy for %s: %v", c.RemoteAddr(), err)
            }
        }(conn)
    }
}