具有 Java 个套接字的 HTTP 客户端

Question

我尝试在 Java 中打开一个 TCP 套接字并向服务器发送 GET 请求 (www.abc.net.au) 并将响应打印到控制台。

客户代码：

import java.util.Scanner;

import java.net.InetAddress;
import java.net.SocketAddress;
import java.net.InetSocketAddress;
import java.net.Socket;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;

public class Client {
    public static void main(String[] args) throws Exception{

        Scanner sc;
        String addressString;
        int port =80;
        int timeoutMs = 30000;
        String temp;

        //Read address from commandline
        sc =new Scanner(System.in);
        System.out.print("Adresse: ");
        addressString = sc.next();
        sc.close();
        //Open socket
        InetAddress addr = InetAddress.getByName(addressString);
        SocketAddress sockaddr = new InetSocketAddress(addr, port);
        Socket socket = new Socket();

        //Connection timeout
        socket.connect(sockaddr,timeoutMs);

        System.out.println( socket.getPort() +"\n");

        //Define input/output
        BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        PrintWriter pw = new PrintWriter(socket.getOutputStream(), true);

        //Send GET request
        pw.print("GET / HTTP/1.1\r\n");
        pw.print("Host: "+ addressString +"\r\n\r\n");
        while((temp=br.readLine())!=null){
            System.out.println(temp);

        }
        //Close Input/Output and Socket
        pw.close();
        br.close();
        socket.close();
    }
}

该代码似乎一直有效，直到它到达 while 之后我得到：

HTTP/1.0 408 Request Time-out
Server: AkamaiGHost
Mime-Version: 1.0
Date: Sun, 07 Oct 2018 15:36:40 GMT
Content-Type: text/html
Content-Length: 218
Expires: Sun, 07 Oct 2018 15:36:40 GMT

<HTML><HEAD>
<TITLE>Request Timeout</TITLE>
</HEAD><BODY>
<H1>Request Timeout</H1>
The server timed out while waiting for the browser's request.<P>
Reference&#32;&#35;2&#46;3d5b6068&#46;1538926600&#46;0
</BODY></HTML>

Process finished with exit code 0

我不明白是什么导致了这个问题，已经在 Whosebug、java2s 和我家里的一本书上寻找答案。尝试其他页面通常以以下结尾：

Process finished with exit code 0

仅此而已。

知道我的请求 missing/incorrect 是什么吗？

感谢每一个提示。

Answer 1

PrintWriter 具有用于存储数据的内部缓冲区，因此当您调用 print 时 - 不会向服务器发送任何内容

来自https://docs.oracle.com/javase/7/docs/api/java/io/PrintWriter.html

Unlike the PrintStream class, if automatic flushing is enabled it will be done only when one of the println, printf, or format methods is invoked, rather than whenever a newline character happens to be output.

因此，您可以使用这些方法代替 print，或者直接调用 flush：

pw.print("GET / HTTP/1.1\r\n");
pw.print("Host: " + addressString + "\r\n\r\n");
pw.flush(); // actually send data to server

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