Click to download Ethernet Basics manual - Grant Industrial Controls
Click to download Ethernet Basics manual - Grant Industrial Controls
Click to download Ethernet Basics manual - Grant Industrial Controls
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TCP/IP 56<br />
3.6 Communication over TCP(UDP)/IP<br />
3.6.1 Client Server model<br />
An internet (TCP/IP) ensures a general communication infrastructure without specifying what<br />
services can be used. TCP/IP provides a basic communication service but this pro<strong>to</strong>col software<br />
is not capable of making or accepting contact from a remote participant. Therefore, two<br />
application programmes have <strong>to</strong> be used for each communication. One application starts the<br />
communication and the other accepts this.<br />
one significant problem: the pro<strong>to</strong>col software cannot tell at all <strong>to</strong> an application programme<br />
that a request for communication has arrived. The communication between two participants<br />
will therefore be based on a model where one application is active (interaction requests)<br />
while the other is passive (listening and possibly accepting). Such a model is currently only<br />
applied <strong>to</strong> communication between two different hosts over TCP/IP and is called the Client<br />
Server model: a Server application waits passively on contact while the Client application<br />
starts the communication actively.<br />
Features of Client software:<br />
• Is an application programme that temporarily becomes a Client when remote access <strong>to</strong><br />
a computer is required but that also carries out local calculations and operations.<br />
• Is directly started by the user and is only carried out for one session.<br />
• Runs locally on the user’s PC<br />
• Establishes active contact with a Server<br />
• If necessary, can access several Servers but establishes active contact with one Server<br />
at a time<br />
• Does not require special hardware or an advanced control system<br />
Features of Server software:<br />
• Is a specially designed application programme that supplies one specific service but<br />
can handle different Clients at the same time.<br />
• Is au<strong>to</strong>matically activated when a system starts and remains active for many sessions<br />
• Waits passively until random, remote Clients look for contact<br />
• Requires some powerful hardware and an advanced control system (depends on the<br />
application type)
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