Java stream socket can only send once

Question

I'm writing a simple download accelerator. The problem is I can send and receive messages once. The next time I try to send and receive message, I get no response froms server. I'm not even sure if I am able to send the second message.

The first message is something like;

*HEAD /TIPS/LAWLER/PANOHOW2.PDF HTTP/1.0\r\n   
HTTP/1.0\r\n  
Connection: close\r\n  
\r\n*

and response is;

*HTTP/1.1 200 OK  
Date: Mon, 24 Jan 2011 10:53:38 GMT  
Server: Apache  
Last-Modified: Tue,  
22 Sep 1998 13:19:52 GMT  
ETag: "1968013-2b4f4-3386e15b6ee00"  
Accept-Ranges: bytes  
Content-Length: 177396  
Connection: close  
Content-Type: application/pdf*

When i attemp to sen message;

GET /TIPS/LAWLER/hedeh/PANOHOW2.PDF HTTP/1.0\r\n  
Range: bytes=0-44349\r\n  
Connection: close\r\n   
\r\n

I get nothing.

What is wrong with my code?

public class Main {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {



            //Parse URL
            String cmd = "http://www.imaging-resource.com"; //Host Name
            if (cmd.contains("http://"))
            {
                cmd = cmd.substring(7); //
                if (cmd.contains("/"))
                {
                    int index = cmd.indexOf("/");
                    cmd = cmd.substring(0, index);
                    System.out.println(cmd);
                }
            }
            String str = "HEAD /TIPS/LAWLER/PANOHOW2.PDF HTTP/1.0\r\nConnection: close\r\n\r\n"; //First message to send




            //Create socket, connect, initialize read and write handlers
            //in, out
            Socket socket = null;           //Create a client socket
            SocketAddress sockaddr = null;
            InetAddress address = null;
            InputStream input = null;      //Input handler
            OutputStream output = null;    //Output handler

            try
            {
                address = InetAddress.getByName(cmd);           //Get ip using host name
                socket = new Socket();                          //Contrusct Socket
                sockaddr = new InetSocketAddress(address, 80);
                //socket.setTcpNoDelay(false);
                socket.connect(sockaddr, 2000);                 //Connect to server set and timeout to 2 sec
            } //End of try Block
            catch (Exception ex)
            {
                Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
                System.out.println(ex);
            } //End of catch Block

             if (!socket.isConnected())
             {
                System.out.println("not connected");
                System.exit(-1);
             }


            //Sending package here
            try
            {
                int c;
                byte[] buf = new byte[65535];
                char[] chr = new char[65535];


                input = socket.getInputStream();            //Input handler is created
                output = socket.getOutputStream();          //Output handler is created
                buf = str.getBytes();                       //HEAD message converted into byte array
                output.write(buf);                          //Sending message to server
                output.flush();
                int counter = 0;


                while ((c = input.read()) != -1)        //Reading received package
                    chr[counter++]=(char)c;


                //input.reset();
                str = new String(chr);                  //For better manipulation, server message is converted to string
                System.out.println(str);

            } catch (IOException e)
            {
                System.err.print(e);
            } //End of catch








            int index = str.indexOf("Content-Length");  //Look for "Content-Length" in response
            str = str.substring(index);                 //Using its beginning index create an substring           
            index = str.indexOf("\r\n");                //Search for end of line
            str = str.substring(0, index);              //Erase end if line chars   - \r\n
            str = str.substring(16, str.length());      //"Content-Length: " 16 chars
            int fileSize = Integer.parseInt(str);       //Lentgh of file is converted to Integer


            int[][] parts = new int[4][2];              //Beginning and en of jobs for threads will be stored here
            int remainder = fileSize;                   //Bytes left to split for rest of the threads will be stored here
            int start = 0;
            int finish = 0;

            for (int i = 0; i < 4; i++)                 //Number of threads many times
            {
                parts[i][0] = start;                        //*******Each threads job Interval(eg. 0-108)
                //System.out.print(parts[i][0] + "-");      //******
                finish += remainder / 4 - i;                //*****
                parts[i][1] = finish;                       //****
                start = finish + 1;                         //***

                if (i + 1 == 4)
                parts[i][1] = fileSize;                     //*
            }

            str = "GET /TIPS/LAWLER/hedeh/PANOHOW2.PDF HTTP/1.0\r\nRange: bytes=" + parts[0][0] + "-" + parts[0][1] + "\r\nConnection: close\r\n\r\n";
            //System.out.println(str);


           if(!socket.isConnected())
           {
               System.out.println("closed");
               try
               {
                    socket.connect(sockaddr, 2000);
               }//End od try
               catch(Exception e){
                System.err.print(e);
                }//End of catch
            }//End of If
           System.out.println("Is Outputhandler closed :"+socket.isOutputShutdown());
           System.out.println("Is Inputhandler closed :"+socket.isInputShutdown());



          try
          {

               int c;
               byte[] buf = new byte[65535];
               char[] chr = new char[65535];


                buf = str.getBytes();                      //Output handler is created
                output.write(buf);                         //Sending message to server
                output.flush();
                int counter = 0;

                if((c = input.read()) != -1)
                {
                    chr[counter++] = (char) c;

                    while ((c = input.read()) != -1)                //Reading received package
                    {
                        System.out.println("response is not -1");
                        chr[counter++]=(char)c;
                    }


                    str = new String(chr);                  //For better manipulation, serve message is converted to string
                    System.out.println("Response "+str);
                }//End of If

                else System.out.println("No Response!");


            }catch(Exception e)
            {System.err.print(e);}

            //Closing open stuff
             try {
                output.close();
                input.close();
                socket.close();
            } catch (Exception e) {
                System.out.println(e);
            }




    }// End of main method
}//End of class definition

Answer 1

The first message is something like;

HTTP/1.0\r\n  

You have to use HTTP version 1.1 to use multiple requests on a single TCP connection.

From the Wikipedia article on HTTP:

In HTTP/0.9 and 1.0, the connection is closed after a single request/response pair. In HTTP/1.1 a keep-alive-mechanism was introduced, where a connection could be reused for more than one request.

---

Also, as @Joachim Sauer points out in the comments, you're explicitly saying Connection: close in your header. :-)

Answer 2

I think that the problem is that you are trying to connect to HTTP server using plain TCP socket. Yes, HTTP is on top of TCP but it is complicated protocol that requires a lot of things to know. I'd suggest you to work with higher level API that implements HTTP protocol and provides you more convenient API.

The simplest example is URL+URLConnection from JDK. Probably better is HttpClient from Jakarta.