Re: Socket & PrintWriter issue-- writing a float to a C client

From:
=?ISO-8859-1?Q?Arne_Vajh=F8j?= <arne@vajhoej.dk>
Newsgroups:
comp.lang.java.programmer
Date:
Fri, 08 Sep 2006 22:11:17 -0400
Message-ID:
<8ppMg.37425$_q4.7958@dukeread09>
Dale King wrote:

"Jean-Francois Briere" <jfbriere@gmail.com> wrote in message
news:1157702176.527004.33610@e3g2000cwe.googlegroups.com...

listener= new ServerSocket(portNumber);
mySocket=listener.accept();
outp = new DataOutputStream(mySocket.getOutputStream());
outp.writeFloat(85.6f);


I hope that was meant as a joke as it is the *WORST* way to do this. It is
non-portable. You are assuming that Java and C use the same binary
representation for their floating point values, which is a completely
unfounded assumption.


Actually the Java code is not that bad.

It sends binary floats using standard IEEE floating
point format in standard network byte order.

Which is a very well defined format that almost
all non embedded computer will understand.

The problem is that the C code did not use ntohl.

The most portable way to send the exact value is to do:

  system.out.println( new BigDecimal( 85.6f ).toString() );


That constructor variant is general considered
bad practice.

Arne

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