Editing POLLHUP polling
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'''This page is a work in progress''' | |||
Recently I've been trying to listen on multiple sockets at once for events like reading or writing. This has worked fine, but as I've tried to listen for a socket close event I've found the documentation poor and often contradictory. This page is my attempt to figure this topic out. | Recently I've been trying to listen on multiple sockets at once for events like reading or writing. This has worked fine, but as I've tried to listen for a socket close event I've found the documentation poor and often contradictory. This page is my attempt to figure this topic out. | ||
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* 1997: Linux 2.1.23pre1 added the poll system call, with no AF_UNIX socket support | * 1997: Linux 2.1.23pre1 added the poll system call, with no AF_UNIX socket support | ||
* 1998: Linux 2.1.106pre added AF_UNIX socket support | * 1998: Linux 2.1.106pre added AF_UNIX socket support | ||
* 2000: Linux 2.3.41pre2 returns POLLIN on empty socket close | * 2000: Linux 2.3.41pre2 returns POLLIN on empty socket close | ||
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* POLLIN if checking | * POLLIN if checking | ||
* POLLHUP always | * POLLHUP always | ||
This is regardless of whether there is data in the socket to read. | This is regardless of whether there is data in the socket to read. | ||
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The history of FreeBSD's behaviour is as follows: | The history of FreeBSD's behaviour is as follows: | ||
* 1997: [https://svnweb.freebsd.org/base? | * 1997: [https://svnweb.freebsd.org/base/head/sys/kern/sys_generic.c?r1=29041&r2=29351 FreeBSD implements poll] based on NetBSD's code. POLLHUP is not returned by sockets | ||
* 2009: | * 2009 July: 7f5dff50646e2 adds POLLHUP | ||
* 2009: | * 2009 August: f2159cc7908d0 | ||
* 2009: | * 2009 August: 74d1c4927a3b7ce785e41e97e33a804f4f8c62ce | ||
* 2018: ad7eb8cad5320 | |||
== OpenBSD == | == OpenBSD == | ||
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* POLLIN if checking | * POLLIN if checking | ||
* POLLHUP always | * POLLHUP always | ||
This is regardless of whether there is data in the socket to read. | This is regardless of whether there is data in the socket to read. | ||
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The history of OpenBSD's behaviour is as follows: | The history of OpenBSD's behaviour is as follows: | ||
* | * TODO | ||
== NetBSD == | == NetBSD == | ||
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== Conclusions == | == Conclusions == | ||
poll can be used to check for socket closure alone on some systems, but it isn't portable. But it's a little more portable than kqueue and epoll? | |||