libcurl Manual curlmultisocket(3)
NAME
curlmultisocket - reads/writes available data
SYNOPSIS
#include
CURLMcode curlmultisocketaction(CURLM * multihandle,
curlsockett sockfd, int evbitmask,
int *runninghandles);
Now deprecated versions:
CURLMcode curlmultisocket(CURLM * multihandle, curlsockett sockfd,
int *runninghandles);
CURLMcode curlmultisocketall(CURLM *multihandle,
int *runninghandles);
DESCRIPTION
Alternative versions of curlmultiperform(3) that allows
the application to pass in the file descriptor/socket that
has been detected to have "action" on it and let libcurl
perform. This lets libcurl avoid having to scan through all
possible file descriptors to check for action.
When the application has detected action on a socket handled
by libcurl, it should call curlmultisocketaction(3) with
the sockfd argument set to the socket with the action. When
the events on a socket are known, they can be passed as an
events bitmask evbitmask by first setting evbitmask to 0,
and then adding using bitwise OR () any combination of
events to be chosen from CURLCSELECTIN, CURLCSELECTOUT
or CURLCSELECTER. When the events on a socket are
unknown, pass 0 instead, and libcurl will test the descrip-
tor internally.
At return, the integer runninghandles points to will con-
tain the number of still running easy handles within the
multi handle. When this number reaches zero, all transfers
are complete/done. Note that when you call
curlmultisocketaction(3) 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
curlmultiinforead(3) to figure out which easy handle that
completed.
The curlmultisocketaction(3) functions inform the appli-
cation about updates in the socket (file descriptor) status
by doing none, one, or multiple calls to the socket callback
function set with the CURLMOPTSOCKETFUNCTION option to
curlmultisetopt(3). They update the status with changes
since the previous time the callback was called.
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libcurl Manual curlmultisocket(3)
Get the timeout time by setting the CURLMOPTIMERFUNCTION
option with curlmultisetopt(3). 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
curlmultisocketaction(3) function with the sockfd argu-
ment set to CURLSOCKETIMEOUT. You can also use the
curlmultitimeout(3) 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.
Usage of curlmultisocket(3) is deprecated, whereas the
function is equivalent to curlmultisocketaction(3) with
evbitmask set to 0.
Force libcurl to (re-)check all its internal sockets and
transfers instead of just a single one by calling
curlmultisocketall(3). Note that there should not be any
reason to use this function!
CALBACK DETAILS
The socket callback function uses a prototype like this
int curlsocketcallback(CURL *easy, /* easy handle */
curlsockett s, /* socket */
int action, /* see values below */
void *userp, /* private callback pointer */
void *socketp); /* private socket pointer */
The callback MUST return 0.
The easy 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 s argument is the actual socket value as you use it
within your system.
The action argument to the callback has one of five values:
CURLPOLNONE (0)
register, not interested in readiness (yet)
CURLPOLIN (1)
register, interested in read readiness
CURLPOLOUT (2)
register, interested in write readiness
CURLPOLINOUT (3)
register, interested in both read and write readi-
ness
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CURLPOLREMOVE (4)
unregister
The socketp argument is a private pointer you have previ-
ously set with curlmultiassign(3) to be associated with
the s socket. If no pointer has been set, socketp will be
NUL. 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 userp argument is a private pointer you have previously
set with curlmultisetopt(3) and the CURLMOPTSOCKETDATA
option.
RETURN VALUE
CURLMcode type, general libcurl multi interface error code.
Legacy: If you receive CURLMCALMULTIPERFORM, this basi-
cally means that you should call curlmultisocket(3) 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".
In modern libcurls, CURLMCALMULTIPERFORM or
CURLMCALMULTISOKCET should not be returned and no appli-
cation needs to care about them.
NOTE that the return code is for the whole multi stack.
Problems still might have occurred on individual transfers
even when one of these functions return OK.
TYPICAL USAGE
1. Create a multi handle
2. Set the socket callback with CURLMOPTSOCKETFUNCTION
3. Set the timeout callback with CURLMOPTIMERFUNCTION, to
get to know what timeout value to use when waiting for
socket activities.
4. Add easy handles with curlmultiaddhandle()
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
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curlmultisocketaction() for the socket(s) that got
action. If no activity is detected and the timeout expires,
call curlmultisocketaction(3) with CURLSOCKETIMEOUT
8. Go back to step 6.
AVAILABILITY
This function was added in libcurl 7.15.4, and is deemed
stable since 7.16.0.
curlmultisocket(3) is deprecated, use
curlmultisocketaction(3) instead!
SEE ALSO
curlmulticleanup(3), curlmultiinit(3),
curlmultifdset(3), curlmultiinforead(3), the
hiperfifo.c example
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
ATRIBUTE TYPE ATRIBUTE VALUE
Availability SUNWcurl
Interface Stability Uncommitted
NOTES
Source for C-URL is available on http:/opensolaris.org.
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