Re: Reliability of writeUTF / readUTF

From:

Joshua Cranmer <Pidgeot18@verizon.invalid>

Newsgroups:

comp.lang.java.programmer

Date:

Tue, 27 Nov 2007 22:09:27 GMT

Message-ID:

<rA03j.44767$9h.9883@trnddc07>

korcs wrote:

If I communicate via Sockets and the Server sends a message in form of
a string, how can a make sure that at the time of reading the message,
I read the whole message and not only a stub of it.

Well, everything is going to be modulo network considerations, but Java
pieces everything together for you in the end through sockets.

Is it all the time correct, or should I use a method to make 100% sure
that I have read the whole message?

(A method could be:

Server side: send first the byte length of the message as a "short"
then the message itself;

Client side: read first the length with the method "readShort" and
then to read exactly as many bytes, as the message length is...)

Does somebody know the official solution for the problem?

From the Javadocs for DataOutputStream's writeUTF:
First, two bytes are written to the output stream as if by the
writeShort method giving the number of bytes to follow. This value is
the number of bytes actually written out, not the length of the string.
[ ... ]

Java already does the message length processing for you (see the
corresponding documentation in DataInput's readUTF if you don't believe me).

--
Beware of bugs in the above code; I have only proved it correct, not
tried it. -- Donald E. Knuth