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    <p>The <code>Standard Serial ports</code> are mapped as /ttyS0,/ttyS1,... as you correctly stated. Generic <code>USB Serial Ports</code> as well as most <code>G3 modems</code> are accessible as <code>/dev/ttyUSB0</code> through <code>/dev/ttyUSB255</code></p> <p>The better way to distinguish if a serial port 'connected' with a modem is to send <code>ATIx</code> commands to the serial port. These are <a href="http://en.wikipedia.org/wiki/Hayes_command_set" rel="nofollow noreferrer">Identity</a> commands that you may use to detect the model name of the device and many other details.</p> <p>First you try to send <code>ATIx</code> command not changing the baud rate. If you do not receive any valid response (<code>ASCII</code> multi-line text followed by <code>OK&lt;CR&gt;&lt;LF&gt;</code> <code>ERROR...&lt;CR&gt;&lt;LF&gt;</code> then you may alter the baud rate and retry. It is better to first set the maximum supported by port speed and then decrease it until you find a modem or you end up with 110 baud or other reasonable limit.</p> <p>There is a way to detect if most likely there is nothing connected to the serial port. The idea behind is to detect the frame error that persists during some reasonable time (tens times to receive a byte at selected baud rate), say 2-3sec. To see how enable/disable frame errors detection look at <code>man termios</code>. Howeever, I am not absolutely sure that in the setup you described this will be possible (from within VM), so you have to try.</p> <p>Also look at this post <a href="https://stackoverflow.com/questions/5347962/how-to-connect-to-a-terminal-to-serial-usb-device-on-ubuntu-10-10">How to connect to a terminal to Serial-USB device on Ubuntu 10.10?</a></p>
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    1. POCheck what serial port i'm using in linux
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    1. COThanks for that Serge. but what if i'm not using modems? e.g like embedded systems that is connected to the said ports how will i know if the serial port is avaialable or not?. Thanks again for answering.
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    2. COterm `embedded` is too wide. Generally speaking if you do not know how the device should respond you can only make an assumption that something is plugged in by analyzing the state of `CD`, `DSR` and `CTS` signals. When there is nothing connected all of them in the same state. However, this is really not reliable.
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    3. COTHanks.. Is my previous way of doing it okay?.. opening and writing to the port? if i can write then it means something is plugged to that serial port?
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