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POCommunication between two applications using Environment Variables
 

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  1. POCommunication between two applications using Environment Variables
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    <h2>Question</h2> <p>How to communicate with another program (for instance, a windows service one) through environment variables (not system or user ones)?</p> <h2>What do we have</h2> <p>Well, I have the following scheme for a data logger:</p> <pre><code>------------------------- -------------------------------- | the things to measure | | the things that do something | ------------------------- -------------------------------- | ^ | sensors | switches V | ------------------------------------------------------------------- | dedicated hardware | ------------------------------------------------------------------- | ^ | | serial communication V | --------------- ------------- | Windows | ------------------------------------&gt; | user | | service | &lt;------------------------------------ | interface | --------------- udp communication ------------- |^ keyboard V| and screen -------- | user | -------- </code></pre> <p>On current development:</p> <ul> <li>windows service is always running when Windows is running</li> <li>user can open and close user interface (of course :p)</li> <li>windows service acquires data from sensors</li> <li>user interface automatic requests data to windows service every 100ms and shows it to user via udp communication through some implemented protocol (we call it <code>GetData()</code> command and response to it)</li> <li>user can send some other commands to change the data to acquire through implemented protocol (we call it <code>SetSensors()</code> command and response to it)</li> </ul> <p>Both user interface and windows service are developed on Borland C+ Builder 6 and use NMUDP component, from FastNet tab, for UDP communication.</p> <h2>What we are thinking to do</h2> <p>Because of some buffer issues and to free udp channel only for sending <code>SetSensors()</code>command and response to it, we are considering that instead of using <code>GetData()</code>:</p> <ul> <li>Windows service would get data from sensors and put them on environment variables</li> <li>the user interface would read them to show to user</li> </ul> <h2>Scheme after doing what we are thinking</h2> <pre><code>------------------------- -------------------------------- | the things to measure | | the things that do something | ------------------------- -------------------------------- | ^ | sensors | switches V | ------------------------------------------------------------------- | dedicated hardware | ------------------------------------------------------------------- | ^ | | serial communication V | --------------- ------------- | | ------------------------------------&gt; | | | | environment variables | | | | (get data from sensors) | | | Windows | | user | | service | | interface | | | | | | | ------------------------------------&gt; | | | | &lt;------------------------------------ | | --------------- udp communication ------------- (send commands to service) |^ keyboard V| and screen -------- | user | -------- </code></pre> <h2>Any way to do that?</h2> <p>We would not use system and user environment variables, because it writes on Windows Registry, i.e., it will save to hard drive and it gets more slow...</p>
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    1. COYou cannot communicate with environment variables, a process can only update their local copy. Use any of the process interop mechanisms available in Windows, like a socket, named pipe or memory mapped file. No point in using UDP, use TCP so you get a delivery guarantee. UDP isn't faster when it doesn't go out on a network.
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