java - 从浏览器发出 GET 请求后通过 java 中的套接字发送文件的正确方法

Question

我正在使用浏览器通过简单地输入地址 127.0.0.1:1501/filename.png 来向服务器发送 get 请求。目的是从服务器下载文件。服务器成功接收请求并加载所选文件，它还进入 while 循环并多次执行 print 方法，这意味着正在发送某些内容，但在“网络”选项卡中检查 google chrome 时我只得到 filename.png失败的我不明白为什么这段代码似乎不起作用。print 是一个简单调用 System.out.println() 方法的方法

public class MainClassServer {
    public static void main(String[] args){
        // TODO Auto-generated method stub
        ServerSocket server = null;
        try {
            server = new ServerSocket();
        } catch (IOException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
        try {
            server.bind(new InetSocketAddress("127.0.0.1", 1501));
        } catch (UnknownHostException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        } catch (IOException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }


        while(true) {
            String message;
            Socket client = null;
            print("Waiting for client...");
            try{
                client = server.accept();
            } catch (Exception e) {
                // TODO: handle exception
                e.printStackTrace();
            }
            BufferedReader reader = null;
            DataOutputStream writer = null;

            try {
                reader = new BufferedReader(new InputStreamReader(client.getInputStream()));
                writer = new DataOutputStream(new BufferedOutputStream(client.getOutputStream()));
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            try {
                message = reader.readLine();

                if(message!=null) {
                    //I get the correct filename with string manipulation
                    // I correctly access the file in fact it exist
                    File file = new File(path);

                    if(file.exists()) {
                        byte[] bytes = new byte[1024];
                        InputStream in = new FileInputStream(path);
                        int count;
                        while ((count = in.read(bytes)) > 0) {
                            //the program print some bytes so it writes something to someone
                            print("Sending " + count + " bytes");
                            writer.write(bytes, 0, count);
                        }
                        writer.flush();
                    }else {
                        print("File does not exsist.");
                    }


                    writer.close();
                    reader.close();
                    server.close();
                    break;  
                }

            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        }
    }


}

Answer 1

浏览器在请求时始终期望返回 HTTP 响应。如果您的客户端是简单的套接字客户端，那么当您在 HTTP 的 DataOutputStream 中编写时，您将获得该文件，至少您需要最小的 HTTP 响应格式。如果您在响应中添加这两个 header ，您可能会得到预期的行为。

if(file.exists()) {
    byte[] bytes = new byte[1024];
    InputStream in = new FileInputStream(path);
    int count;
    // Setting HTTP response headers
    writer.writeBytes("HTTP/1.0 200 OK\r\n");
    writer.writeBytes("Content-Type: image/jpeg\r\n");
    writer.writeBytes("\r\n");
    while ((count = in.read(bytes)) > 0) {
        //the program print some bytes so it writes something to someone
        print("Sending " + count + " bytes");
        writer.write(bytes, 0, count);
    }
    writer.flush();
}else {
    print("File does not exsist.");
}