From 31c6e7af6af315d923b29f490f27c038e18712a8 Mon Sep 17 00:00:00 2001 From: Dan Fandrich Date: Mon, 15 Apr 2013 22:26:18 +0200 Subject: FAQ: mention that the network connection can be monitored Also note the prohibition on sharing handles across threads. --- docs/FAQ | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) (limited to 'docs/FAQ') diff --git a/docs/FAQ b/docs/FAQ index fe291526f..2b15254db 100644 --- a/docs/FAQ +++ b/docs/FAQ @@ -728,7 +728,7 @@ FAQ When passing on a URL to curl to use, it may respond that the particular protocol is not supported or disabled. The particular way this error message is phrased is because curl doesn't make a distinction internally of whether - a particular protocol is not supported (ie never got any code added that + a particular protocol is not supported (i.e. never got any code added that knows how to speak that protocol) or if it was explicitly disabled. curl can be built to only support a given set of protocols, and the rest would then be disabled or not supported. @@ -1055,11 +1055,11 @@ FAQ 4.19 Why doesn't cURL return an error when the network cable is unplugged? - Unplugging the cable is not an error situation. The TCP/IP protocol stack + Unplugging a cable is not an error situation. The TCP/IP protocol stack was designed to be fault tolerant, so even though there may be a physical break somewhere the connection shouldn't be affected, just possibly delayed. Eventually, the physical break will be fixed or the data will be - re-routed around the physical problem. + re-routed around the physical problem through another path. In such cases, the TCP/IP stack is responsible for detecting when the network connection is irrevocably lost. Since with some protocols it is @@ -1077,6 +1077,12 @@ FAQ falls too low, and --connect-timeout and --max-time can be used to put an overall timeout on the connection phase or the entire transfer. + A libcurl-using application running in a known physical environment (e.g. + an embedded device with only a single network connection) may want to act + immediately if its lone network connection goes down. That can be achieved + by having the application monitor the network connection on its own using an + OS-specific mechanism, then signalling libcurl to abort (see also item 5.13). + 5. libcurl Issues @@ -1086,7 +1092,9 @@ FAQ We have written the libcurl code specifically adjusted for multi-threaded programs. libcurl will use thread-safe functions instead of non-safe ones if - your system has such. + your system has such. Note that you must never share the same handle in + multiple threads. + If you use a OpenSSL-powered libcurl in a multi-threaded environment, you need to provide one or two locking functions: -- cgit v1.2.3