sending multiple byte array over the socket

Question

I want to send multiple byte array from the client and server ?

I was able to send/Receive one byte array from client and send / Receive one byte array from server :

My code is like this :

server :

 Socket sock=null;
  ByteArrayOutputStream input=null;
  OutputStream out=null;
    InputStream in=null;
  try{
      ServerSocket server_sock=new ServerSocket(2972);


    sock=server_sock.accept(); 

   in = 
       sock.getInputStream();
    out=sock.getOutputStream();
    }catch(IOException e){
      System.out.println(e.getMessage());
  }
 String word="";

  //1-Receive

  try{

    ByteArrayOutputStream serverinput=new ByteArrayOutputStream();
 int len=0;
byte[] buf=new byte[1000];
        while ((len = in.read(buf))>=0) {
              serverinput.write(buf, 0, len);

        }

      sock.shutdownInput();

        word=new String(serverinput.toByteArray());
    System.out.println("Client send 1"+word);

    }catch(Exception e){
      System.out.println(e.getMessage());
  }


   String st="Server is a king";
try{ 
   out.write(st.getBytes());

   out.flush();

}catch(Exception e){
      System.out.println(e.getMessage());
  }

client :

 Socket sock=null;
    OutputStream out=null;
    InputStream in=null;


  try{
      sock=new Socket("127.0.0.1",2972);
      }catch(IOException e){
      System.out.println(e.getMessage());
  }


String word="Hellow World"  ;
    try{
    in = 
       sock.getInputStream();
    out=sock.getOutputStream();
    }catch(IOException e){
      System.out.println(e.getMessage());
  }

//1- send
   try{

       System.out.println("Your string is"+word+"converted to byte"+word.getBytes());

    out.write(word.getBytes());
    out.flush();
 sock.shutdownOutput();
    }catch(Exception e){
      System.out.println(e.getMessage());
  }

    try{  ByteArrayOutputStream serverinput=new ByteArrayOutputStream();
 int len=0;
byte[] buf=new byte[1000];
        while ((len = in.read(buf))>=0) {
              serverinput.write(buf, 0, len);


        }
    System.out.println("server send 1 "+new String(serverinput.toByteArray()));
     System.out.println("Your string is"+word+"converted to byte"+word.getBytes());

    }catch(Exception e){
      System.out.println(e.getMessage());
  }

This code is working fine for one submitting from client and server but it does not work when I want to send / receive more byte array ?

It is working only when I use shutdown because both client and server reading and writing to the data.

Therefore, I can not use the socket channel again ... is there is alternative solution? ...that does not lead to deadlock.

Mark Lapasa · Accepted Answer · 2014-12-31 03:49:55Z

13

The problem you have is that you don't currently have any way to say when one byte array ends and the next one starts. (In your "one array" solution, the end of the byte array corresponds to the end of stream. And of course, once the stream has been ended / closed, it cannot be reopened without creating a new Socket, etcetera.)

The simple way to solve this is as follows, using DataOutputStream and DataInputStream pairs wrapped around the respective socket streams:

To send a byte array:
1. Convert data to bytes.
2. Send the byte array size using the DataOutputStream.writeInt(int) method.
3. Send the byte array using DataOutputStream.write(byte[]) method.
To receive a byte array:
1. Receive the byte array size using the DataInputStream.readInt() method.
2. Allocate a byte array of the required size.
3. Receive the bytes into the byte array using the DataInputStream.read(byte[], int, int) method ... repeatedly until you've gotten all of the bytes.

By sending the size of the byte array at the front, you tell the receiver how many bytes to read. You can repeat this process as many times as you need. The sender can indicate to the receiver that there are no more byte arrays to send by simply closing the socket stream.

Note - this is pseudo-code. I assume that you are capable of turning it into working Java.

Don't forget to insert BufferedInputStreams and BufferedOutputStreams into the respective stream chains ... to reduce system call overheads.

edited Dec 31, 2014 at 3:49

Mark Lapasa

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answered Apr 29, 2011 at 4:45

Stephen C

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3 Comments

gumuruh Over a year ago

@Javalover... eh, would youd mind to share the code up there after you worked it out?

Stephen C Over a year ago

@gumuruh - Why? Any competent Java programmer should be able to code that with ZERO help.

gumuruh Over a year ago

don't be angry @StephenC... I got it now. :D

Ted Hopp · Accepted Answer · 2011-04-29 02:25:54Z

0

Try wrapping your socket streams in DataInputStream and DataOutputStream. That should allow you to do what you want.

answered Apr 29, 2011 at 2:25

Ted Hopp

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1 Comment

Fredrik Over a year ago

@Javalover Then you didn't do it correctly and it is very hard for us to help you unless you update the post to reflect what you did.

Saurabh Gokhale · Accepted Answer · 2011-04-29 02:27:49Z

0

You should really have a look at this tutorial : Reading from and Writing to a Socket

It seems to outline how to read and write to a socket. The reading should be as easy as creating a server socket and listening on the port you expect and then waiting for data.

answered Apr 29, 2011 at 2:27

Saurabh Gokhale

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1 Comment

Programming_Lover Over a year ago

this is not writing or reading by socket , it is transforming the data over the network

Cris CodeCruncher · Accepted Answer · 2014-02-18 03:31:41Z

0

You could also create an object that would hold your byte array and send it out with ObjectOutputStream, then use the writeObject(Object) method to send the info.

answered Feb 18, 2014 at 3:31

Cris CodeCruncher

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