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Linux/php serial port read - How to stop fread() waiting forever if no new data?

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Last Modified: 2013-11-19
I'm working through exactly the same issue as described by skaap2k. (11/04/07 12:01 AM, ID: 22503690)

I am using a Linux (Ubuntu) server and PHP as a web server. The solution offered appears to be for a command line version of PHP, and doesn't work in my web server.

In short, I need to read and write to a GSM modem via the serial port using php. Writing is working fine.

Reading using fread() of /dev/ttyS1 stalls the server until the required number of bytes set in fread() and a CR is received.

I need to return from checking the serial port with a null if there is no new data. I'm happy to pick a byte at a time from the serial buffer and assemble it into a string in php.

Any suggestions welcome!
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