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Re: Re: Reading/Writing files across networks

• To: mathgroup at smc.vnet.net
• Subject: [mg36042] Re: [mg36024] Re: Reading/Writing files across networks
• From: "Hermann Schmitt" <schmitther at netcologne.de>
• Date: Wed, 14 Aug 2002 05:35:10 -0400 (EDT)
• References: <200208130922.FAA10054@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

Hello,
The following is possible:
Assume Mathematica runs on machine A, then you can install Java (see JLink
User Guide p.20) on machine B. In this way you can execute Java programs on
machine B from machine A. Those programs may read data on machine B and
transfer the data to machine A, automatically.
Hermann Schmitt
----- Original Message -----
From: "Rolf Mertig" <rolf at mertig.com>
To: mathgroup at smc.vnet.net
Subject: [mg36042] [mg36024] Re: Reading/Writing files across networks


> >Hello,
> > we're running Mathematica 4.2 under Linux.
> >Since we're working alot across networks we wonder if it is possible
> >with Mathematica to read and write files directly between the Linux
> > cluster where we've Mathematica installed and another Unix machine at
> > another domain (provided the permissions are set). I.e., is it
> > possible by calling OpenRead[...] with the appropriate options to open
> >a file on another domain machine for reading ? Perhaps by using pipes
> >?! The same applies to OpenWrite, Import, Export...
> >Many thanks, regards
> >Justus
>
> Hi,
> no, Mathematica is (unfortunately) still not integrated enough with Java.
> However, you can use a modified GetURL (originally from the JLink manual)
and
> write wrapper funcionts (like the NetIfiy below) around it.
> I.e., you would have to put give users on your cluster
> (local, and even proxied) access to an Apache server with the
> filesystem where the Mathematica (or other files) live visible.
>
> E.g.:
>
> Netify[func_, url_String/;StringMatchQ[url,"http:*"], args___]:=
> Block[{imp,tmp},tmp = GetURL[url];
imp=func[tmp,args];DeleteFile[tmp];imp ];
>
> Netify[Get, "http://www.mertig.com/mathdepot/misc/Isolate.m";]
> (* this is the same as calling  Get["Isolate.m"]  if Isolate.m would be
> lokal*)
>
>
> Netify[Import,"http://www.linux.de/pics/Linux.de-logo.gif","GIF"]//Show
> (* this just displays a gif *)
>
>
> (*Here the GetURL funcion: *)
>
> Needs["JLink`"]
> $ProxyHost=None;
> $ProxyPort=8080;
>
> Options[GetURL]={ProxyHost :> $ProxyHost,
>       ProxyPort :> $ProxyPort};
> GetURL[url_String, opts___?OptionQ] :=
>     JavaBlock[
>         Module[{u, stream, numRead, outFile, buf, prxyHost, prxyPort},
>             {prxyHost, prxyPort} = {ProxyHost, ProxyPort} /.
> Flatten[{opts}] /. Options[GetURL];
>             StartJava[];
>             If[StringQ[prxyHost],
>                 (* Set properties to force use of proxy. *)
>                 SetInternetProxy[prxyHost, prxyPort]
>             ];
>             u = JavaNew["java.net.URL", url];
>             (* This is where the error will show up if the URL is not
valid.
>                A Java exception will be thrown during openStream, which
>                causes the method to return $Failed.
>             *)
>             stream = u@openStream[];
>             If[stream === $Failed, Return[$Failed]];
>             buf = JavaNew["[B", 5000]; (* 5000 is an arbitrary buffer size
*)
>             outFile = OpenTemporary[DOSTextFormat->False];
>             While[(numRead = stream@read[buf]) > 0,
>                 WriteString[outFile, FromCharacterCode[If[# < 0, # + 256,
#]&
> /@ Take[Val[buf], numRead]]]
>             ];
>             stream@close[];
>             Close[outFile]   (* Close returns the filename *)
>         ]
>     ]
>
> You can find other useful applications of GetURL at
> http://www.mertig.com/neu/HTMLLinks/index_5.html
>
> One could even think of "Netifying" complete complex Mathematica packages
and
> applications.
> Kind of "ASP" (application service provider).
> Now, if someone pays me I'll set such a system up for them ... (of course
> paying attention to license issues etc.;  maybe the normal Mathematica
license
> should just fade out and in the near ".Net-like webservice futer"
> there should be only webMathematica licenses anymore).
>
> Regards from Berlin-Mitte,
>
> Rolf Mertig
>
> Mertig Consulting
> http://www.mertig.com
>

• References:
  • Re: Reading/Writing files across networks
    • From: Rolf Mertig <rolf@mertig.com>