简单的Web服务器实现：GoLang

Question

I am trying to implement a simple web server using Go. I expected "Hello World" to be displayed on the client's browser at the URL "http://127.0.0.1.12000/".

I have tried the following code but ended up with errors.

package main

import "net"
import "fmt"
import "bufio"

// import "strings"
// only needed below for sample processing

func main() {
    fmt.Println("Launching server...")

    // listen on all interfaces
    ln, err := net.Listen("tcp", ":12000")
    if err != nil {
        fmt.Println("Launching error1...")
        return
    }
    // run loop forever (or until ctrl-c)
    for {
        // accept connection on port
        conn, err := ln.Accept()
        if err != nil {
            fmt.Println("Launching error2...")
            return
        }

        // will listen for message to process ending in newline (
)
        message, err := bufio.NewReader(conn).ReadString('
')

        if err != nil {
            fmt.Println("Launching error3...")
            newmessage := "Hello World!"
            conn.Write([]byte(newmessage + "
"))
            return
        }

        // output message received
        fmt.Print("Message Received:", string(message))

        // sample process for string received
        newmessage := "Hello World!"
        conn.Write([]byte(newmessage + "
"))
    }
}

When I tried to execute the code, the command line shows the following, but there is no output on browser..

Launching server...
Message Received:GET / HTTP/1.1
Message Received:GET / HTTP/1.1

Am I missing anything? Did I make any mistakes?

Answer 1

Just to add some information here.. That that isn't a simple server that you're writing. You're trying to write an HTTP server without the net/http package. This is nontrivial. Perhaps you want an echo server instead?

Your browser wants a properly formatted HTTP response. That means you can't just write a random string to the connection and expect it to know what to do with it. Here is a wikipedia to the HTTP protocol description (I don't intend to describe an entire protocol in a SO answer).

If you want just a bare bones answer that should work:

HTTP/1.1 200 OK
Content-Type: text/plain; charset=UTF-8;
Content-Length: LENGTH OF BODY HERE

BODY

Note that headers are separated by and the last header is followed by two: .

So this:

conn.Write([]byte("HTTP/1.1 200 OK
"))
conn.Write([]byte("Content-Type: text/plain; charset=UTF-8
"))
newmessage := "Hello World!"
conn.Write([]byte("Content-Length: " + strconv.Itoa(len(newmessage)) + "

"))
conn.Write([]byte(newmessage + "
"))

Also, I guess since this is a protocol issue I could also let you know that the typical HTTP port is 80 and the alternative/testing one is 8080. Just some added convention for your knowledge I guess.