--- name: "Danga::Socket" section: "3pm" platform: "linux" package: "perl-danga-socket" version: "1.62-7" release: "Arch Linux 2026-11-01" platforms: ["linux"] url: "https://new.carta.tech/Danga::Socket" --- # Danga::Socket(3pm) Event loop and event-driven async socket base class ## NAME Danga::Socket - Event loop and event-driven async socket base class ## SYNOPSIS ``` package My::Socket use Danga::Socket; use base ('Danga::Socket'); use fields ('my_attribute'); sub new { my My::Socket $self = shift; $self = fields::new($self) unless ref $self; $self->SUPER::new( @_ ); $self->{my_attribute} = 1234; return $self; } sub event_err { ... } sub event_hup { ... } sub event_write { ... } sub event_read { ... } sub close { ... } $my_sock->tcp_cork($bool); # write returns 1 if all writes have gone through, or 0 if there # are writes in queue $my_sock->write($scalar); $my_sock->write($scalarref); $my_sock->write(sub { ... }); # run when previous data written $my_sock->write(undef); # kick-starts # read max $bytecount bytes, or undef on connection closed $scalar_ref = $my_sock->read($bytecount); # watch for writability. not needed with ->write(). write() # will automatically turn on watch_write when you wrote too much # and turn it off when done $my_sock->watch_write($bool); # watch for readability $my_sock->watch_read($bool); # if you read too much and want to push some back on # readable queue. (not incredibly well-tested) $my_sock->push_back_read($buf); # scalar or scalar ref Danga::Socket->AddOtherFds(..); Danga::Socket->SetLoopTimeout($millisecs); Danga::Socket->DescriptorMap(); Danga::Socket->WatchedSockets(); # count of DescriptorMap keys Danga::Socket->SetPostLoopCallback($code); Danga::Socket->EventLoop(); ``` ## DESCRIPTION This is an abstract base class for objects backed by a socket which provides the basic framework for event-driven asynchronous IO, designed to be fast. Danga::Socket is both a base class for objects, and an event loop. Callers subclass Danga::Socket. Danga::Socket's constructor registers itself with the Danga::Socket event loop, and invokes callbacks on the object for readability, writability, errors, and other conditions. Because Danga::Socket uses the "fields" module, your subclasses must too. ## MORE INFO For now, see servers using Danga::Socket for guidance. For example: perlbal, mogilefsd, or ddlockd. ## API Note where "`"CLASS"`" is used below, normally you would call these methods as: ``` Danga::Socket->method(...); ``` However using a subclass works too. The CLASS methods are all methods for the event loop part of Danga::Socket, whereas the object methods are all used on your subclasses. ### "CLASS-\>Reset()" Reset all state ### "CLASS-\>HaveEpoll()" Returns a true value if this class will use IO::Epoll for async IO. ### "CLASS-\>WatchedSockets()" Returns the number of file descriptors which are registered with the global poll object. ### "CLASS-\>EnableProfiling()" Turns profiling on, clearing current profiling data. ### "CLASS-\>DisableProfiling()" Turns off profiling, but retains data up to this point ### "CLASS-\>ProfilingData()" Returns reference to a hash of data in format: ``` ITEM => [ utime, stime, #calls ] ``` ### "CLASS-\>ToClose()" Return the list of sockets that are awaiting **close()** at the end of the current event loop. ### "CLASS-\>OtherFds( \[%fdmap\] )" Get/set the hash of file descriptors that need processing in parallel with the registered Danga::Socket objects. ### "CLASS-\>AddOtherFds( \[%fdmap\] )" Add fds to the OtherFds hash for processing. ### "CLASS-\>SetLoopTimeout( $timeout )" Set the loop timeout for the event loop to some value in milliseconds. A timeout of 0 (zero) means poll forever. A timeout of -1 means poll and return immediately. ### "CLASS-\>DebugMsg( $format, @args )" Print the debugging message specified by the `"sprintf"`-style *format* and *args* ### "CLASS-\>AddTimer( $seconds, $coderef )" Add a timer to occur `$seconds` from now. `$seconds` may be fractional, but timers are not guaranteed to fire at the exact time you ask for. Returns a timer object which you can call `"$timer->cancel"` on if you need to. ### "CLASS-\>DescriptorMap()" Get the hash of Danga::Socket objects keyed by the file descriptor (fileno) they are wrapping. Returns a hash in list context or a hashref in scalar context. ### "CLASS-\>EventLoop()" Start processing IO events. In most daemon programs this never exits. See `"PostLoopCallback"` below for how to exit the loop. ### "CLASS-\>SetPostLoopCallback( CODEREF )" Sets post loop callback function. Pass a subref and it will be called every time the event loop finishes. Return 1 (or any true value) from the sub to make the loop continue, 0 or false and it will exit. The callback function will be passed two parameters: \\%DescriptorMap, \\%OtherFds. ### OBJECT METHODS ### "CLASS-\>new( $socket )" Create a new Danga::Socket subclass object for the given *socket* which will react to events on it during the `"EventLoop"`. This is normally (always?) called from your subclass via: ``` $class->SUPER::new($socket); ``` ### "$obj-\>tcp\_cork( $boolean )" Turn TCP\_CORK on or off depending on the value of *boolean*. ### "$obj-\>steal\_socket()" Basically returns our socket and makes it so that we don't try to close it, but we do remove it from epoll handlers. THIS CLOSES `$self`. It is the same thing as calling close, except it gives you the socket to use. ### "$obj-\>close( \[$reason\] )" Close the socket. The *reason* argument will be used in debugging messages. ### "$obj-\>sock()" Returns the underlying IO::Handle for the object. ### "$obj-\>set\_writer\_func( CODEREF )" Sets a function to use instead of `syswrite()` when writing data to the socket. ### "$obj-\>write( $data )" Write the specified data to the underlying handle. *data* may be scalar, scalar ref, code ref (to run when there), or undef just to kick-start. Returns 1 if writes all went through, or 0 if there are writes in queue. If it returns 1, caller should stop waiting for 'writable' events) ### "$obj-\>push\_back\_read( $buf )" Push back *buf* (a scalar or scalarref) into the read stream. Useful if you read more than you need to and want to return this data on the next "read". ### "$obj-\>read( $bytecount )" Read at most *bytecount* bytes from the underlying handle; returns scalar ref on read, or undef on connection closed. If you call read more than once and no more data available after the first call, a scalar ref to an empty string is returned. ### (VIRTUAL) "$obj-\>event\_read()" Readable event handler. Concrete derivatives of Danga::Socket should provide an implementation of this. The default implementation will die if called. ### (VIRTUAL) "$obj-\>event\_err()" Error event handler. Concrete derivatives of Danga::Socket should provide an implementation of this. The default implementation will die if called. ### (VIRTUAL) "$obj-\>event\_hup()" 'Hangup' event handler. Concrete derivatives of Danga::Socket should provide an implementation of this. The default implementation will die if called. ### "$obj-\>event\_write()" Writable event handler. Concrete derivatives of Danga::Socket may wish to provide an implementation of this. The default implementation calls `write()` with an `"undef"`. ### "$obj-\>watch\_read( $boolean )" Turn 'readable' event notification on or off. ### "$obj-\>watch\_write( $boolean )" Turn 'writable' event notification on or off. ### "$obj-\>dump\_error( $message )" Prints to STDERR a backtrace with information about this socket and what lead up to the dump\_error call. ### "$obj-\>debugmsg( $format, @args )" Print the debugging message specified by the `"sprintf"`-style *format* and *args*. ### "$obj-\>peer\_ip\_string()" Returns the string describing the peer's IP ### "$obj-\>peer\_addr\_string()" Returns the string describing the peer for the socket which underlies this object in form "ip:port" ### "$obj-\>local\_ip\_string()" Returns the string describing the local IP ### "$obj-\>local\_addr\_string()" Returns the string describing the local end of the socket which underlies this object in form "ip:port" ### "$obj-\>as\_string()" Returns a string describing this socket. ## AUTHORS Brad Fitzpatrick \ - author Michael Granger \ - docs, testing Mark Smith \ - contributor, heavy user, testing Matt Sergeant \ - kqueue support, docs, timers, other bits ## BUGS Not documented enough (but isn't that true of every project?). tcp\_cork only works on Linux for now. No BSD push/nopush support. ## LICENSE License is granted to use and distribute this module under the same terms as Perl itself.