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MathLink query - LinkWrite blocks???

• To: mathgroup at smc.vnet.net
• Subject: [mg18456] MathLink query - LinkWrite blocks???
• From: "Julie Abraham" <jabraham at vetinari.demon.co.uk>
• Date: Wed, 7 Jul 1999 00:11:37 -0400
• Sender: owner-wri-mathgroup at wolfram.com

Hi - I'm experimenting with MathLink (using Mathematica v.4.0 on Windows 95)
and am finding it behaves in a manner that I don't expect from my reading of
section 2.12.6 of Wolfram's Mathematica book.

I'm trying to communicate between two separate kernel sessions running on
the same machine. I open the link with LinkCreate[] on the first kernel and
then access the link on the second kernel with LinkConnect[]. I can
communicate between the two kernels this way with no problems. However, I
find that the first time I send information from the first kernel to the
second kernel with LinkWrite[], the LinkWrite[] call "blocks" (ie. the first
kernel freezes up) until the second kernel reads the information with link
using LinkRead[].

However (and this is the part that really has me stumped), *subsequent*
attempts to write to the link from the first kernel to the second kernel do
NOT block. I write to the link with LinkWrite[] and immediately the kernel
is ready for more input. According to the Mathematica book, LinkWrite[]
should never block (ie. not even the first time).

Is this the normal behaviour for LinkWrite[]?

Yours confusedly,

Bob Abraham
Institute of Astronomy
Cambridge University