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Diffstat (limited to 'docs/libcurl/curl_multi_socket_action.3')
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diff --git a/docs/libcurl/curl_multi_socket_action.3 b/docs/libcurl/curl_multi_socket_action.3 new file mode 100644 index 00000000..7a1ffbc7 --- /dev/null +++ b/docs/libcurl/curl_multi_socket_action.3 @@ -0,0 +1,129 @@ +.\" $Id: curl_multi_socket_action.3,v 1.3 2010-02-01 21:42:44 bagder Exp $ +.\" +.TH curl_multi_socket_action 3 "9 Jul 2006" "libcurl 7.16.0" "libcurl Manual" +.SH NAME +curl_multi_socket_action \- reads/writes available data given an action +.SH SYNOPSIS +.nf +#include <curl/curl.h> + +CURLMcode curl_multi_socket_action(CURLM * multi_handle, + curl_socket_t sockfd, int ev_bitmask, + int *running_handles); +.fi +.SH DESCRIPTION +When the application has detected action on a socket handled by libcurl, it +should call \fIcurl_multi_socket_action(3)\fP with the \fBsockfd\fP argument +set to the socket with the action. When the events on a socket are known, they +can be passed as an events bitmask \fBev_bitmask\fP by first setting +\fBev_bitmask\fP to 0, and then adding using bitwise OR (|) any combination of +events to be chosen from CURL_CSELECT_IN, CURL_CSELECT_OUT or +CURL_CSELECT_ERR. When the events on a socket are unknown, pass 0 instead, and +libcurl will test the descriptor internally. + +At return, the integer \fBrunning_handles\fP points to will contain the number +of running easy handles within the multi handle. When this number reaches +zero, all transfers are complete/done. When you call +\fIcurl_multi_socket_action(3)\fP on a specific socket and the counter +decreases by one, it DOES NOT necessarily mean that this exact socket/transfer +is the one that completed. Use \fIcurl_multi_info_read(3)\fP to figure out +which easy handle that completed. + +The \fBcurl_multi_socket_action(3)\fP functions inform the application about +updates in the socket (file descriptor) status by doing none, one, or multiple +calls to the socket callback function set with the CURLMOPT_SOCKETFUNCTION +option to \fIcurl_multi_setopt(3)\fP. They update the status with changes +since the previous time the callback was called. + +Get the timeout time by setting the \fICURLMOPT_TIMERFUNCTION\fP option with +\fIcurl_multi_setopt(3)\fP. Your application will then get called with +information on how long to wait for socket actions at most before doing the +timeout action: call the \fBcurl_multi_socket_action(3)\fP function with the +\fBsockfd\fP argument set to CURL_SOCKET_TIMEOUT. You can also use the +\fIcurl_multi_timeout(3)\fP function to poll the value at any given time, but +for an event-based system using the callback is far better than relying on +polling the timeout value. +.SH "CALLBACK DETAILS" + +The socket \fBcallback\fP function uses a prototype like this +.nf + + int curl_socket_callback(CURL *easy, /* easy handle */ + curl_socket_t s, /* socket */ + int action, /* see values below */ + void *userp, /* private callback pointer */ + void *socketp); /* private socket pointer */ + +.fi +The callback MUST return 0. + +The \fIeasy\fP argument is a pointer to the easy handle that deals with this +particular socket. Note that a single handle may work with several sockets +simultaneously. + +The \fIs\fP argument is the actual socket value as you use it within your +system. + +The \fIaction\fP argument to the callback has one of five values: +.RS +.IP "CURL_POLL_NONE (0)" +register, not interested in readiness (yet) +.IP "CURL_POLL_IN (1)" +register, interested in read readiness +.IP "CURL_POLL_OUT (2)" +register, interested in write readiness +.IP "CURL_POLL_INOUT (3)" +register, interested in both read and write readiness +.IP "CURL_POLL_REMOVE (4)" +unregister +.RE + +The \fIsocketp\fP argument is a private pointer you have previously set with +\fIcurl_multi_assign(3)\fP to be associated with the \fIs\fP socket. If no +pointer has been set, socketp will be NULL. This argument is of course a +service to applications that want to keep certain data or structs that are +strictly associated to the given socket. + +The \fIuserp\fP argument is a private pointer you have previously set with +\fIcurl_multi_setopt(3)\fP and the CURLMOPT_SOCKETDATA option. +.SH "RETURN VALUE" +CURLMcode type, general libcurl multi interface error code. + +Before version 7.20.0: If you receive \fICURLM_CALL_MULTI_PERFORM\fP, this +basically means that you should call \fIcurl_multi_socket_action(3)\fP again +before you wait for more actions on libcurl's sockets. You don't have to do it +immediately, but the return code means that libcurl may have more data +available to return or that there may be more data to send off before it is +"satisfied". + +The return code from this function is for the whole multi stack. Problems +still might have occurred on individual transfers even when one of these +functions return OK. +.SH "TYPICAL USAGE" +1. Create a multi handle + +2. Set the socket callback with CURLMOPT_SOCKETFUNCTION + +3. Set the timeout callback with CURLMOPT_TIMERFUNCTION, to get to know what +timeout value to use when waiting for socket activities. + +4. Add easy handles with curl_multi_add_handle() + +5. Provide some means to manage the sockets libcurl is using, so you can check +them for activity. This can be done through your application code, or by way +of an external library such as libevent or glib. + +6. Wait for activity on any of libcurl's sockets, use the timeout value your +callback has been told + +7, When activity is detected, call curl_multi_socket_action() for the +socket(s) that got action. If no activity is detected and the timeout expires, +call \fIcurl_multi_socket_action(3)\fP with \fICURL_SOCKET_TIMEOUT\fP + +8. Go back to step 6. +.SH AVAILABILITY +This function was added in libcurl 7.15.4, and is deemed stable since 7.16.0. +.SH "SEE ALSO" +.BR curl_multi_cleanup "(3), " curl_multi_init "(3), " +.BR curl_multi_fdset "(3), " curl_multi_info_read "(3), " +.BR "the hiperfifo.c example" |