How to use network programming functions in Go language to implement HTTP server downloading files?

How to use network programming functions in Go language to implement HTTP server download files?

Network programming plays an important role in modern software development. Using the Go language, we can easily implement an HTTP server so that it can provide file download functions. This article will introduce how to use the network programming functions in the Go language to implement a simple HTTP server to realize the file download function.

1. Import required packages

First, we need to import some required packages. In Go language, we can use "net/http" and "os" packages to implement HTTP server and file operations.

package main

import (
    "fmt"
    "net/http"
    "os"
)

2. Implementing the HTTP server

Next, we will create a processor function to handle HTTP requests from the client. In this example, we will implement a simple download function. The client passes the file name through a GET request, and the server will return the file to the client.

func fileHandler(w http.ResponseWriter, r *http.Request) {
    // 获取文件名
    filename := r.URL.Query().Get("filename")
  
    // 打开文件
    file, err := os.Open(filename)
    if err != nil {
        // 文件不存在或无法打开，返回404
        http.NotFound(w, r)
        return
    }
    defer file.Close()
  
    // 设置响应头
    fileInfo, _ := file.Stat()
    w.Header().Set("Content-Disposition", "attachment; filename="+filename)
    w.Header().Set("Content-Type", "application/octet-stream")
    w.Header().Set("Content-Length", fmt.Sprintf("%d", fileInfo.Size()))
  
    // 发送文件给客户端
    http.ServeContent(w, r, filename, fileInfo.ModTime(), file)
}

In this processor function, we first get the file name passed by the client. Then we open the file and do error checking. If the file does not exist or cannot be opened, we will return a 404 error to the client. If the file opens successfully, we set response headers including the downloaded file name, type, and length. Finally, we use the http.ServeContent function to send the file content to the client.

3. Register processor function

In the main function, we need to register the processor function and bind it to a path, So that clients can access the service through this path. In this example, we register the handler function on the "/download" path.

func main() {
    http.HandleFunc("/download", fileHandler)
    http.ListenAndServe(":8000", nil)
}

We use the http.HandleFunc function to register the processor function on the specified path. Then, we call the http.ListenAndServe function to listen to the specified port in order to receive requests from the client.

4. Run the server

Now that we have completed the implementation of the HTTP server, we can run the server and test the download functionality. Run go run main.go on the command line to start the server. The server will listen on port 8000 and wait for client requests.

When the client accesses http://localhost:8000/download?filename=test.txt, the server will try to open the file named test.txt file and send it to the client. If the file does not exist, the server will return a 404 error.

Through the above code example, we can see that it is very simple to implement an HTTP server to download files using the network programming functions provided by the Go language. Through this example, we can understand the powerful functions of Go language in network programming and how to use these functions to achieve actual application requirements.

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