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-rw-r--r-- | docs/FAQ | 30 |
1 files changed, 29 insertions, 1 deletions
@@ -74,6 +74,7 @@ FAQ 4.16 My HTTP POST or PUT requests are slow! 4.17 Non-functional connect timeouts on Windows 4.18 file:// URLs containing drive letters (Windows, NetWare) + 4.19 Why doesn't cURL return an error when the network cable is unplugged? 5. libcurl Issues 5.1 Is libcurl thread-safe? @@ -944,6 +945,31 @@ FAQ In either case, cURL should now be looking for the correct file. + 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 + 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. + + In such cases, the TCP/IP stack is responsible for detecting when the + network connection is irrevocably lost. Since with some protocols it is + perfectly legal for the client wait indefinitely for data, the stack may + never report a problem, and even when it does, it can take up to 20 minutes + for it to detect an issue. The curl option --keepalive-time enables + keep-alive support in the TCP/IP stack which makes it periodically probe the + connection to make sure it is still available to send data. That should + reliably detect any TCP/IP network failure. + + But even that won't detect the network going down before the TCP/IP + connection is established (e.g. during a DNS lookup) or using protocols that + don't use TCP. To handle those situations, curl offers a number of timeouts + on its own. --speed-limit/--speed-time will abort if the data transfer rate + 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. + + 5. libcurl Issues 5.1 Is libcurl thread-safe? @@ -1182,7 +1208,9 @@ FAQ to do "LIST -a" or similar to see them. The application thus needs to parse the LIST output. One such existing - list parser is available at http://cr.yp.to/ftpparse.html + list parser is available at http://cr.yp.to/ftpparse.html Versions of + libcurl since 7.21.0 also provide the ability to specify a wildcard to + download multiple files from one FTP directory. 6. License Issues |