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copied!<blockquote> <ol> <li>How does one create a persistant Server <-> Client connection,as described above.</li> </ol> </blockquote> <p>You've got several choices: you can write a threaded server, where a single 'process' with mostly shared memory executes multiple threads of execution, and each thread has some thread-local storage for e.g. <code>client</code>. Or, you could write a multi-process server, where each client connection gets its own independent process via <code>fork(2)</code> (which pretty much means it runs on Unix-only, as Windows attempts to implement <code>fork(2)</code> never work well). Or, you could write an event-loop based state machine, and use <code>select(2)</code> or <code>poll(2)</code> or <code>epoll(4)</code> to manage which clients are readable, writable, and have errors.</p> <p>Choosing between them might seem difficult, <a href="http://www.kegel.com/c10k.html" rel="nofollow">but there are guidelines available</a>. I'd like to suggest that -small- systems, where you're only expected to have 20-30 simultaneous clients, can be very well handled via threaded or forked servers. If you wish to go beyond that number of simultaneous clients, you should use a tool like <a href="https://github.com/eventmachine/eventmachine/wiki" rel="nofollow">EventMachine</a> or <a href="http://monkey.org/~provos/libevent/" rel="nofollow">libevent</a> to write your server. (Which may or may not be easier to maintain anyway.)</p> <blockquote> <p>2) Is there a better way of keeping a server open, without using loop [because I feel like I've commited murder by creating an endless loop]</p> </blockquote> <p>Endless loops are quite fine :) but sometimes it makes sense to offer a way to restart servers or terminate them via <code>signal(7)</code>s or specialized command interfaces.</p> <blockquote> <p>3) Why does it stay suspended like that without client.close in the server? Does the server buffer the messages before it sends them?</p> </blockquote> <p>Ah, <strong>here</strong> is the question you really needed -- TCP will try to <em>buffer</em> the results of multiple packets from the server, and due to the potential need to fragment too-large packets mid-route, you, as a client, have <em>no guarantees</em> that any kind of datagram boundaries are preserved.</p> <p>Chances are <em>very</em> good that your server's TCP/IP stack waited a tiny bit before sending the first packet to see if more data is coming soon. (It often does.) It probably coalesced the <em>two</em> calls to <code>client.print()</code> into a single TCP packet. Your client calls <code>client.read()</code> <em>twice</em>, but there is probably only enough data for <em>one</em> read. If you wanted your TCP stream to send the first packet <em>immediately</em>, you could look into setting the <code>TCP_NODELAY</code> socket option to disable this small delay. (But it might not help all on its own; you might need to use it in conjunction with <code>TCP_CORK</code> to try to "bottle up" all the writes until you explicitly flush them. This is probably an awful idea.)</p> <p>A better option would be to re-write your client to be aware of the <em>protocol</em> between your server and client; it needs to read input into a buffer, parse the buffer to find 'complete messages', consume those messages, and then return to its main event loop.</p> <p>Maybe your protocol is to read / write ASCII or UTF-8 terminated with <code>"\n"</code> characters; in that case, you can change <code>print</code> to <code>puts</code> or add the <code>\n</code> in the right places, and change <code>read()</code> to <code>readline()</code>. (This would let the standard IO library handle your protocol for you.) Another approach would be to send data with length+data pairs, and await the correct length of data.</p>

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