Send byte array through socket between perl and Java

Question

I have a big issue with my java client.

Server: perl, with IO::Socket;

$n is the socket

    sub listen{    
 while(1){
  my $n = $_[0]->accept();
  my $thread;
  my $thread2;
  $thread = threads->create('talk', $n);
  $thread2 = threads->create('recu', $n);
 }

When a client send a message to the server

    sub talk{
 my $n = $_[0];
 while(<$n>){
  print $n $_;
 }

In 'talk' the server send the client message back to the client

Client: Java, in a Thread I send a byte array ->

static DataOutputStream os;

...

     public static void handleMsg(byte [] b){
  try {
   os.write(b);
  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }

 }

->

<pre><code>
    byte[] buff = new byte[]{10,4};
ThreadListen.handleMsg(buff);
</code></pre>
I receive in the run() method only the first byte in the array (10)
<pre><code>
    public void run(){
  DataInputStream in = null;
  try{
   in = new DataInputStream(s.getInputStream());
  } catch (IOException e) {
   System.out.println("in or out failed");
   System.exit(-1);
  }

  while(true){
   try{
    byte[] buff = new byte[6];
    int b = in.read(buff, 0, buff.length);
   }catch (IOException e) {
    System.out.println("Read failed");
    System.exit(-1);
   }
  }
 }

If I try to send

byte[] buff = new byte[]{50,4};
ThreadListen.handleMsg(buff);

I receive nothing!!!

Did i missed something, I assume that if I send

byte[] buff = new byte[]{50,4};

I should receive 50,4 :)

Thanks,

araqnid · Accepted Answer · 2010-12-06 12:05:04Z

4

Your Perl code is doing <$n> so it's fetching data line-by-line. since 10 is the line-feed character, receiving a {10,4} sequence means it gets an empty line (which it prints back) and then a character 4. Even if it receives that (some debug messages in the Perl code would help), the print back to the socket may not complete if the socket is block-buffered (likely the default) without flushing the socket filehandle.

answered Dec 6, 2010 at 12:05

araqnid

135k25 gold badges164 silver badges139 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

JohnJohnGa Over a year ago

Understand - why when I send 10,4 I got 10 but when I send 50,4, I received nothing...

araqnid Over a year ago

<$n> fetches line-by-line: it won't return anything until it encounters an end-of-line character (10) or the socket is closed by the other side. You need to use read, as mentioned by Hasturkun.

JohnJohnGa Over a year ago

You mean something like this?:sub talkRead{ my $n = $_[0]; my $data; while(1==1){ $n->read($data, 1024); print $n $data; } }

JohnJohnGa Over a year ago

Are you sure it is only a Perl issue? I try with read but I got nothing, I will try again :)

araqnid Over a year ago

the Java output stream might be buffered as well? DataOutputStream doesn't do buffering, though, so if you put that straight on top of the socket it shouldn't. I tend to use strace (on linux) to see the system calls to read/write etc. to debug exactly what's getting sent through in these situations.

Hasturkun · Accepted Answer · 2010-12-06 12:02:55Z

1

You may want to use read explicitly (instead of readline implicitly, which as the name suggests reads up to the end of the line, or EOF) to read from the socket.

answered Dec 6, 2010 at 12:02

Hasturkun

36.7k6 gold badges78 silver badges109 bronze badges

Collectives™ on Stack Overflow

Send byte array through socket between perl and Java

2 Answers 2

5 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

5 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related