Reading and Writing to a Socket for HTTP

The following example sends a request to an http server using a socket's output stream; then it reads the response using the socket's input stream. HTTP servers close the connection when they've sent the response.

import java.net.*;
import java.io.*;


public class Grabber {

  public static void main(String[] args) {

    int port = 80;

    for (int i = 0; i < args.length; i++) {
      try {
         URL u = new URL(args[i]);
         if (u.getPort() != -1) port = u.getPort();
         if (!(u.getProtocol().equalsIgnoreCase("http"))) {
           System.err.println("Sorry. I only understand http.");
           continue;
         }
         Socket s = new Socket(u.getHost(), port);
         OutputStream theOutput = s.getOutputStream();
         // no auto-flushing
         PrintWriter pw = new PrintWriter(theOutput, false);
         // native line endings are uncertain so add them manually
         pw.print("GET " + u.getFile() + " HTTP/1.0\r\n");
         pw.print("Accept: text/plain, text/html, text/*\r\n");
         pw.print("\r\n");
         pw.flush();
         InputStream in = s.getInputStream();
         InputStreamReader isr = new InputStreamReader(in);
         BufferedReader br = new BufferedReader(isr);
         int c;
         while ((c = br.read()) != -1) {
           System.out.print((char) c);
         }
      }
      catch (MalformedURLException e) {
        System.err.println(args[i] + " is not a valid URL");
      }
      catch (IOException e) {
        System.err.println(e);
      }

    }

  }

}

This is the beginning of a typical response:

utopia% java Grabber http://students.poly.edu:80
HTTP/1.0 200 OK
Date: Thu, 17 Apr 1997 20:11:14 GMT
Server: Apache/1.1.3
Content-type: text/html

<title>Polytechnic University's Student Council Server</title>
<body bgcolor="white" link=#0000dd vlink=#0000dd>

<img src="http://www.poly.edu/images/poly_3d.jpeg" alt="">

How does this differ from essentially the same program we wrote a little earlier that used URL instead of sockets?

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Last Modified December 15, 1999
Copyright 1997-1999 Elliotte Rusty Harold
elharo@metalab.unc.edu