AnyEvent::Handle - non-blocking I/O on file handles via AnyEvent
use AnyEvent; use AnyEvent::Handle; my $cv = AnyEvent->condvar; my $hdl; $hdl = new AnyEvent::Handle fh => \*STDIN, on_error => sub { my ($hdl, $fatal, $msg) = @_; warn "got error $msg\n"; $hdl->destroy; $cv->send; ); # send some request line $hdl->push_write ("getinfo\015\012"); # read the response line $hdl->push_read (line => sub { my ($hdl, $line) = @_; warn "got line <$line>\n"; $cv->send; }); $cv->recv;
This module is a helper module to make it easier to do event-based I/O on filehandles.
The AnyEvent::Intro tutorial contains some well-documented AnyEvent::Handle examples.
In the following, when the documentation refers to of "bytes" then this means characters. As sysread and syswrite are used for all I/O, their treatment of characters applies to this module as well.
At the very minimum, you should specify fh or connect, and the on_error callback.
fh
connect
on_error
All callbacks will be invoked with the handle object as their first argument.
The constructor supports these arguments (all as key => value pairs).
key => value
The filehandle this AnyEvent::Handle object will operate on. NOTE: The filehandle will be set to non-blocking mode (using AnyEvent::Util::fh_nonblocking) by the constructor and needs to stay in that mode.
AnyEvent::Util::fh_nonblocking
Try to connect to the specified host and service (port), using AnyEvent::Socket::tcp_connect. The $host additionally becomes the default peername.
AnyEvent::Socket::tcp_connect
$host
peername
You have to specify either this parameter, or fh, above.
It is possible to push requests on the read and write queues, and modify properties of the stream, even while AnyEvent::Handle is connecting.
When this parameter is specified, then the on_prepare, on_connect_error and on_connect callbacks will be called under the appropriate circumstances:
on_prepare
on_connect_error
on_connect
This (rarely used) callback is called before a new connection is attempted, but after the file handle has been created. It could be used to prepare the file handle with parameters required for the actual connect (as opposed to settings that can be changed when the connection is already established).
The return value of this callback should be the connect timeout value in seconds (or 0, or undef, or the empty list, to indicate the default timeout is to be used).
0
undef
This callback is called when a connection has been successfully established.
The actual numeric host and port (the socket peername) are passed as parameters, together with a retry callback.
When, for some reason, the handle is not acceptable, then calling $retry will continue with the next conenction target (in case of multi-homed hosts or SRV records there can be multiple connection endpoints). When it is called then the read and write queues, eof status, tls status and similar properties of the handle are being reset.
$retry
In most cases, ignoring the $retry parameter is the way to go.
This callback is called when the conenction could not be established. $! will contain the relevant error code, and $message a message describing it (usually the same as "$!").
$!
$message
"$!"
If this callback isn't specified, then on_error will be called with a fatal error instead.
This is the error callback, which is called when, well, some error occured, such as not being able to resolve the hostname, failure to connect or a read error.
Some errors are fatal (which is indicated by $fatal being true). On fatal errors the handle object will be destroyed (by a call to -> destroy) after invoking the error callback (which means you are free to examine the handle object). Examples of fatal errors are an EOF condition with active (but unsatisifable) read watchers (EPIPE) or I/O errors. In cases where the other side can close the connection at their will it is often easiest to not report EPIPE errors in this callback.
$fatal
-> destroy
EPIPE
AnyEvent::Handle tries to find an appropriate error code for you to check against, but in some cases (TLS errors), this does not work well. It is recommended to always output the $message argument in human-readable error messages (it's usually the same as "$!").
Non-fatal errors can be retried by simply returning, but it is recommended to simply ignore this parameter and instead abondon the handle object when this callback is invoked. Examples of non-fatal errors are timeouts ETIMEDOUT) or badly-formatted data (EBADMSG).
ETIMEDOUT
EBADMSG
On callback entrance, the value of $! contains the operating system error code (or ENOSPC, EPIPE, ETIMEDOUT, EBADMSG or EPROTO).
ENOSPC
EPROTO
While not mandatory, it is highly recommended to set this callback, as you will not be notified of errors otherwise. The default simply calls croak.
croak
This sets the default read callback, which is called when data arrives and no read request is in the queue (unlike read queue callbacks, this callback will only be called when at least one octet of data is in the read buffer).
To access (and remove data from) the read buffer, use the ->rbuf method or access the $handle->{rbuf} member directly. Note that you must not enlarge or modify the read buffer, you can only remove data at the beginning from it.
->rbuf
$handle->{rbuf}
When an EOF condition is detected then AnyEvent::Handle will first try to feed all the remaining data to the queued callbacks and on_read before calling the on_eof callback. If no progress can be made, then a fatal error will be raised (with $! set to EPIPE).
on_read
on_eof
Note that, unlike requests in the read queue, an on_read callback doesn't mean you require some data: if there is an EOF and there are outstanding read requests then an error will be flagged. With an on_read callback, the on_eof callback will be invoked.
Set the callback to be called when an end-of-file condition is detected, i.e. in the case of a socket, when the other side has closed the connection cleanly, and there are no outstanding read requests in the queue (if there are read requests, then an EOF counts as an unexpected connection close and will be flagged as an error).
For sockets, this just means that the other side has stopped sending data, you can still try to write data, and, in fact, one can return from the EOF callback and continue writing data, as only the read part has been shut down.
If an EOF condition has been detected but no on_eof callback has been set, then a fatal error will be raised with $! set to <0>.
This sets the callback that is called when the write buffer becomes empty (or when the callback is set and the buffer is empty already).
To append to the write buffer, use the ->push_write method.
->push_write
This callback is useful when you don't want to put all of your write data into the queue at once, for example, when you want to write the contents of some file to the socket you might not want to read the whole file into memory and push it into the queue, but instead only read more data from the file when the write queue becomes empty.
If non-zero, then these enables an "inactivity" timeout: whenever this many seconds pass without a successful read or write on the underlying file handle (or a call to timeout_reset), the on_timeout callback will be invoked (and if that one is missing, a non-fatal ETIMEDOUT error will be raised).
timeout_reset
on_timeout
There are three variants of the timeouts that work fully independent of each other, for both read and write, just read, and just write: timeout, rtimeout and wtimeout, with corresponding callbacks on_timeout, on_rtimeout and on_wtimeout, and reset functions timeout_reset, rtimeout_reset, and wtimeout_reset.
timeout
rtimeout
wtimeout
on_rtimeout
on_wtimeout
rtimeout_reset
wtimeout_reset
Note that timeout processing is also active when you currently do not have any outstanding read or write requests: If you plan to keep the connection idle then you should disable the timout temporarily or ignore the timeout in the on_timeout callback, in which case AnyEvent::Handle will simply restart the timeout.
Zero (the default) disables this timeout.
Called whenever the inactivity timeout passes. If you return from this callback, then the timeout will be reset as if some activity had happened, so this condition is not fatal in any way.
If defined, then a fatal error will be raised (with $! set to ENOSPC) when the read buffer ever (strictly) exceeds this size. This is useful to avoid some forms of denial-of-service attacks.
For example, a server accepting connections from untrusted sources should be configured to accept only so-and-so much data that it cannot act on (for example, when expecting a line, an attacker could send an unlimited amount of data without a callback ever being called as long as the line isn't finished).
When disabled (the default), then push_write will try to immediately write the data to the handle, if possible. This avoids having to register a write watcher and wait for the next event loop iteration, but can be inefficient if you write multiple small chunks (on the wire, this disadvantage is usually avoided by your kernel's nagle algorithm, see no_delay, but this option can save costly syscalls).
push_write
no_delay
When enabled, then writes will always be queued till the next event loop iteration. This is efficient when you do many small writes per iteration, but less efficient when you do a single write only per iteration (or when the write buffer often is full). It also increases write latency.
When doing small writes on sockets, your operating system kernel might wait a bit for more data before actually sending it out. This is called the Nagle algorithm, and usually it is beneficial.
In some situations you want as low a delay as possible, which can be accomplishd by setting this option to a true value.
The default is your opertaing system's default behaviour (most likely enabled), this option explicitly enables or disables it, if possible.
The default read block size (the amount of bytes this module will try to read during each loop iteration, which affects memory requirements). Default: 8192.
8192
Sets the amount of bytes (default: 0) that make up an "empty" write buffer: If the write reaches this size or gets even samller it is considered empty.
Sometimes it can be beneficial (for performance reasons) to add data to the write buffer before it is fully drained, but this is a rare case, as the operating system kernel usually buffers data as well, so the default is good in almost all cases.
If non-zero (default: 3600), then the destructor of the AnyEvent::Handle object will check whether there is still outstanding write data and will install a watcher that will write this data to the socket. No errors will be reported (this mostly matches how the operating system treats outstanding data at socket close time).
3600
This will not work for partial TLS data that could not be encoded yet. This data will be lost. Calling the stoptls method in time might help.
stoptls
A string used to identify the remote site - usually the DNS hostname (not IDN!) used to create the connection, rarely the IP address.
Apart from being useful in error messages, this string is also used in TLS peername verification (see verify_peername in AnyEvent::TLS). This verification will be skipped when peername is not specified or undef.
verify_peername
When this parameter is given, it enables TLS (SSL) mode, that means AnyEvent will start a TLS handshake as soon as the conenction has been established and will transparently encrypt/decrypt data afterwards.
All TLS protocol errors will be signalled as EPROTO, with an appropriate error message.
TLS mode requires Net::SSLeay to be installed (it will be loaded automatically when you try to create a TLS handle): this module doesn't have a dependency on that module, so if your module requires it, you have to add the dependency yourself.
Unlike TCP, TLS has a server and client side: for the TLS server side, use accept, and for the TLS client side of a connection, use connect mode.
accept
You can also provide your own TLS connection object, but you have to make sure that you call either Net::SSLeay::set_connect_state or Net::SSLeay::set_accept_state on it before you pass it to AnyEvent::Handle. Also, this module will take ownership of this connection object.
Net::SSLeay::set_connect_state
Net::SSLeay::set_accept_state
At some future point, AnyEvent::Handle might switch to another TLS implementation, then the option to use your own session object will go away.
IMPORTANT: since Net::SSLeay "objects" are really only integers, passing in the wrong integer will lead to certain crash. This most often happens when one uses a stylish tls => 1 and is surprised about the segmentation fault.
tls => 1
See the ->starttls method for when need to start TLS negotiation later.
->starttls
Use the given AnyEvent::TLS object to create the new TLS connection (unless a connection object was specified directly). If this parameter is missing, then AnyEvent::Handle will use AnyEvent::Handle::TLS_CTX.
AnyEvent::TLS
AnyEvent::Handle::TLS_CTX
Instead of an object, you can also specify a hash reference with key => value pairs. Those will be passed to AnyEvent::TLS to create a new TLS context object.
This callback will be invoked when the TLS/SSL handshake has finished. If $success is true, then the TLS handshake succeeded, otherwise it failed (on_stoptls will not be called in this case).
$success
on_stoptls
The session in $handle->{tls} can still be examined in this callback, even when the handshake was not successful.
$handle->{tls}
TLS handshake failures will not cause on_error to be invoked when this callback is in effect, instead, the error message will be passed to on_starttls.
on_starttls
Without this callback, handshake failures lead to on_error being called, as normal.
Note that you cannot call starttls right again in this callback. If you need to do that, start an zero-second timer instead whose callback can then call ->starttls again.
starttls
When a SSLv3/TLS shutdown/close notify/EOF is detected and this callback is set, then it will be invoked after freeing the TLS session. If it is not, then a TLS shutdown condition will be treated like a normal EOF condition on the handle.
The session in $handle->{tls} can still be examined in this callback.
This callback will only be called on TLS shutdowns, not when the underlying handle signals EOF.
This is the json coder object used by the json read and write types.
json
If you don't supply it, then AnyEvent::Handle will create and use a suitable one (on demand), which will write and expect UTF-8 encoded JSON texts.
Note that you are responsible to depend on the JSON module if you want to use this functionality, as AnyEvent does not have a dependency itself.
This method returns the file handle used to create the AnyEvent::Handle object.
Replace the current on_error callback (see the on_error constructor argument).
Replace the current on_eof callback (see the on_eof constructor argument).
Replace the current on_timeout, on_rtimeout or on_wtimeout callback, or disables the callback (but not the timeout) if $cb = undef. See the timeout constructor argument and method.
$cb
Enables or disables the current autocork behaviour (see autocork constructor argument). Changes will only take effect on the next write.
autocork
Enables or disables the no_delay setting (see constructor argument of the same name for details).
Replace the current on_starttls callback (see the on_starttls constructor argument).
Replace the current on_stoptls callback (see the on_stoptls constructor argument).
Configures the rbuf_max setting (undef disables it).
rbuf_max
Configures (or disables) the inactivity timeout.
Reset the activity timeout, as if data was received or sent.
These methods are cheap to call.
AnyEvent::Handle manages two queues per handle, one for writing and one for reading.
The write queue is very simple: you can add data to its end, and AnyEvent::Handle will automatically try to get rid of it for you.
When data could be written and the write buffer is shorter then the low water mark, the on_drain callback will be invoked.
on_drain
Sets the on_drain callback or clears it (see the description of on_drain in the constructor).
Queues the given scalar to be written. You can push as much data as you want (only limited by the available memory), as AnyEvent::Handle buffers it independently of the kernel.
AnyEvent::Handle
Instead of formatting your data yourself, you can also let this module do the job by specifying a type and type-specific arguments.
Predefined types are (if you have ideas for additional types, feel free to drop by and tell us):
Formats the given value as netstring (http://cr.yp.to/proto/netstrings.txt, this is not a recommendation to use them).
An octet string prefixed with an encoded length. The encoding $format uses the same format as a Perl pack format, but must specify a single integer only (only one of cCsSlLqQiInNvVjJw is allowed, plus an optional !, < or > modifier).
$format
pack
cCsSlLqQiInNvVjJw
!
<
>
Encodes the given hash or array reference into a JSON object. Unless you provide your own JSON object, this means it will be encoded to JSON text in UTF-8.
JSON objects (and arrays) are self-delimiting, so you can write JSON at one end of a handle and read them at the other end without using any additional framing.
The generated JSON text is guaranteed not to contain any newlines: While this module doesn't need delimiters after or between JSON texts to be able to read them, many other languages depend on that.
A simple RPC protocol that interoperates easily with others is to send JSON arrays (or objects, although arrays are usually the better choice as they mimic how function argument passing works) and a newline after each JSON text:
$handle->push_write (json => ["method", "arg1", "arg2"]); # whatever $handle->push_write ("\012");
An AnyEvent::Handle receiver would simply use the json read type and rely on the fact that the newline will be skipped as leading whitespace:
$handle->push_read (json => sub { my $array = $_[1]; ... });
Other languages could read single lines terminated by a newline and pass this line into their JSON decoder of choice.
Freezes the given reference using Storable and writes it to the handle. Uses the nfreeze format.
nfreeze
Sometimes you know you want to close the socket after writing your data before it was actually written. One way to do that is to replace your on_drain handler by a callback that shuts down the socket (and set low_water_mark to 0). This method is a shorthand for just that, and replaces the on_drain callback with:
low_water_mark
sub { shutdown $_[0]{fh}, 1 } # for push_shutdown
This simply shuts down the write side and signals an EOF condition to the the peer.
You can rely on the normal read queue and on_eof handling afterwards. This is the cleanest way to close a connection.
This function (not method) lets you add your own types to push_write. Whenever the given type is used, push_write will invoke the code reference with the handle object and the remaining arguments.
type
The code reference is supposed to return a single octet string that will be appended to the write buffer.
Note that this is a function, and all types registered this way will be global, so try to use unique names.
The read queue is more complex than the write queue. It can be used in two ways, the "simple" way, using only on_read and the "complex" way, using a queue.
In the simple case, you just install an on_read callback and whenever new data arrives, it will be called. You can then remove some data (if enough is there) from the read buffer ($handle->rbuf). Or you cna leave the data there if you want to accumulate more (e.g. when only a partial message has been received so far).
$handle->rbuf
In the more complex case, you want to queue multiple callbacks. In this case, AnyEvent::Handle will call the first queued callback each time new data arrives (also the first time it is queued) and removes it when it has done its job (see push_read, below).
push_read
This way you can, for example, push three line-reads, followed by reading a chunk of data, and AnyEvent::Handle will execute them in order.
Example 1: EPP protocol parser. EPP sends 4 byte length info, followed by the specified number of bytes which give an XML datagram.
# in the default state, expect some header bytes $handle->on_read (sub { # some data is here, now queue the length-header-read (4 octets) shift->unshift_read (chunk => 4, sub { # header arrived, decode my $len = unpack "N", $_[1]; # now read the payload shift->unshift_read (chunk => $len, sub { my $xml = $_[1]; # handle xml }); }); });
Example 2: Implement a client for a protocol that replies either with "OK" and another line or "ERROR" for the first request that is sent, and 64 bytes for the second request. Due to the availability of a queue, we can just pipeline sending both requests and manipulate the queue as necessary in the callbacks.
When the first callback is called and sees an "OK" response, it will unshift another line-read. This line-read will be queued before the 64-byte chunk callback.
unshift
# request one, returns either "OK + extra line" or "ERROR" $handle->push_write ("request 1\015\012"); # we expect "ERROR" or "OK" as response, so push a line read $handle->push_read (line => sub { # if we got an "OK", we have to _prepend_ another line, # so it will be read before the second request reads its 64 bytes # which are already in the queue when this callback is called # we don't do this in case we got an error if ($_[1] eq "OK") { $_[0]->unshift_read (line => sub { my $response = $_[1]; ... }); } }); # request two, simply returns 64 octets $handle->push_write ("request 2\015\012"); # simply read 64 bytes, always $handle->push_read (chunk => 64, sub { my $response = $_[1]; ... });
This replaces the currently set on_read callback, or clears it (when the new callback is undef). See the description of on_read in the constructor.
Returns the read buffer (as a modifiable lvalue).
You can access the read buffer directly as the ->{rbuf} member, if you want. However, the only operation allowed on the read buffer (apart from looking at it) is removing data from its beginning. Otherwise modifying or appending to it is not allowed and will lead to hard-to-track-down bugs.
->{rbuf}
NOTE: The read buffer should only be used or modified if the on_read, push_read or unshift_read methods are used. The other read methods automatically manage the read buffer.
unshift_read
Append the given callback to the end of the queue (push_read) or prepend it (unshift_read).
The callback is called each time some additional read data arrives.
It must check whether enough data is in the read buffer already.
If not enough data is available, it must return the empty list or a false value, in which case it will be called repeatedly until enough data is available (or an error condition is detected).
If enough data was available, then the callback must remove all data it is interested in (which can be none at all) and return a true value. After returning true, it will be removed from the queue.
Instead of providing a callback that parses the data itself you can chose between a number of predefined parsing formats, for chunks of data, lines etc.
Invoke the callback only once $octets bytes have been read. Pass the data read to the callback. The callback will never be called with less data.
$octets
Example: read 2 bytes.
$handle->push_read (chunk => 2, sub { warn "yay ", unpack "H*", $_[1]; });
The callback will be called only once a full line (including the end of line marker, $eol) has been read. This line (excluding the end of line marker) will be passed to the callback as second argument ($line), and the end of line marker as the third argument ($eol).
$eol
$line
The end of line marker, $eol, can be either a string, in which case it will be interpreted as a fixed record end marker, or it can be a regex object (e.g. created by qr), in which case it is interpreted as a regular expression.
qr
The end of line marker argument $eol is optional, if it is missing (NOT undef), then qr|\015?\012| is used (which is good for most internet protocols).
qr|\015?\012|
Partial lines at the end of the stream will never be returned, as they are not marked by the end of line marker.
Makes a regex match against the regex object $accept and returns everything up to and including the match.
$accept
Example: read a single line terminated by '\n'.
$handle->push_read (regex => qr<\n>, sub { ... });
If $reject is given and not undef, then it determines when the data is to be rejected: it is matched against the data when the $accept regex does not match and generates an EBADMSG error when it matches. This is useful to quickly reject wrong data (to avoid waiting for a timeout or a receive buffer overflow).
$reject
Example: expect a single decimal number followed by whitespace, reject anything else (not the use of an anchor).
$handle->push_read (regex => qr<^[0-9]+\s>, qr<[^0-9]>, sub { ... });
If $skip is given and not undef, then it will be matched against the receive buffer when neither $accept nor $reject match, and everything preceding and including the match will be accepted unconditionally. This is useful to skip large amounts of data that you know cannot be matched, so that the $accept or $reject regex do not have to start matching from the beginning. This is purely an optimisation and is usually worth only when you expect more than a few kilobytes.
$skip
Example: expect a http header, which ends at \015\012\015\012. Since we expect the header to be very large (it isn't in practise, but...), we use a skip regex to skip initial portions. The skip regex is tricky in that it only accepts something not ending in either \015 or \012, as these are required for the accept regex.
\015\012\015\012
$handle->push_read (regex => qr<\015\012\015\012>, undef, # no reject qr<^.*[^\015\012]>, sub { ... });
A netstring (http://cr.yp.to/proto/netstrings.txt, this is not an endorsement).
Throws an error with $! set to EBADMSG on format violations.
For example, DNS over TCP uses a prefix of n (2 octet network order), EPP uses a prefix of N (4 octtes).
n
N
Example: read a block of data prefixed by its length in BER-encoded format (very efficient).
$handle->push_read (packstring => "w", sub { my ($handle, $data) = @_; });
Reads a JSON object or array, decodes it and passes it to the callback. When a parse error occurs, an EBADMSG error will be raised.
If a json object was passed to the constructor, then that will be used for the final decode, otherwise it will create a JSON coder expecting UTF-8.
This read type uses the incremental parser available with JSON version 2.09 (and JSON::XS version 2.2) and above. You have to provide a dependency on your own: this module will load the JSON module, but AnyEvent does not depend on it itself.
Since JSON texts are fully self-delimiting, the json read and write types are an ideal simple RPC protocol: just exchange JSON datagrams. See the json write type description, above, for an actual example.
Deserialises a Storable frozen representation as written by the storable write type (BER-encoded length prefix followed by nfreeze'd data).
storable
Raises EBADMSG error if the data could not be decoded.
This function (not method) lets you add your own types to push_read.
Whenever the given type is used, push_read will invoke the code reference with the handle object, the callback and the remaining arguments.
The code reference is supposed to return a callback (usually a closure) that works as a plain read callback (see ->push_read ($cb)).
->push_read ($cb)
It should invoke the passed callback when it is done reading (remember to pass $handle as first argument as all other callbacks do that).
$handle
For examples, see the source of this module (perldoc -m AnyEvent::Handle, search for register_read_type)).
register_read_type
In rare cases you actually do not want to read anything from the socket. In this case you can call stop_read. Neither on_read nor any queued callbacks will be executed then. To start reading again, call start_read.
stop_read
start_read
Note that AnyEvent::Handle will automatically start_read for you when you change the on_read callback or push/unshift a read callback, and it will automatically stop_read for you when neither on_read is set nor there are any read requests in the queue.
These methods will have no effect when in TLS mode (as TLS doesn't support half-duplex connections).
Instead of starting TLS negotiation immediately when the AnyEvent::Handle object is created, you can also do that at a later time by calling starttls.
Starting TLS is currently an asynchronous operation - when you push some write data and then call ->starttls then TLS negotiation will start immediately, after which the queued write data is then sent.
The first argument is the same as the tls constructor argument (either "connect", "accept" or an existing Net::SSLeay object).
tls
"connect"
"accept"
The second argument is the optional AnyEvent::TLS object that is used when AnyEvent::Handle has to create its own TLS connection object, or a hash reference with key => value pairs that will be used to construct a new context.
The TLS connection object will end up in $handle->{tls}, the TLS context in $handle->{tls_ctx} after this call and can be used or changed to your liking. Note that the handshake might have already started when this function returns.
$handle->{tls_ctx}
Due to bugs in OpenSSL, it might or might not be possible to do multiple handshakes on the same stream. Best do not attempt to use the stream after stopping TLS.
Shuts down the SSL connection - this makes a proper EOF handshake by sending a close notify to the other side, but since OpenSSL doesn't support non-blocking shut downs, it is not guarenteed that you can re-use the stream afterwards.
Shuts down the handle object as much as possible - this call ensures that no further callbacks will be invoked and as many resources as possible will be freed. Any method you will call on the handle object after destroying it in this way will be silently ignored (and it will return the empty list).
Normally, you can just "forget" any references to an AnyEvent::Handle object and it will simply shut down. This works in fatal error and EOF callbacks, as well as code outside. It does NOT work in a read or write callback, so when you want to destroy the AnyEvent::Handle object from within such an callback. You MUST call ->destroy explicitly in that case.
->destroy
Destroying the handle object in this way has the advantage that callbacks will be removed as well, so if those are the only reference holders (as is common), then one doesn't need to do anything special to break any reference cycles.
The handle might still linger in the background and write out remaining data, as specified by the linger option, however.
linger
This function creates and returns the AnyEvent::TLS object used by default for TLS mode.
The context is created by calling AnyEvent::TLS without any arguments.
That's because AnyEvent::Handle keeps a reference to itself when handling read or write callbacks.
It is only safe to "forget" the reference inside EOF or error callbacks, from within all other callbacks, you need to explicitly call the ->destroy method.
Unlike, say, TCP, TLS connections do not consist of two independent communication channels, one for each direction. Or put differently. The read and write directions are not independent of each other: you cannot write data unless you are also prepared to read, and vice versa.
This can mean than, in TLS mode, you might get on_error or on_eof callback invocations when you are not expecting any read data - the reason is that AnyEvent::Handle always reads in TLS mode.
During the connection, you have to make sure that you always have a non-empty read-queue, or an on_read watcher. At the end of the connection (or when you no longer want to use it) you can call the destroy method.
destroy
If you just want to read your data into a perl scalar, the easiest way to achieve this is by setting an on_read callback that does nothing, clearing the on_eof callback and in the on_error callback, the data will be in $_[0]{rbuf}:
$_[0]{rbuf}
$handle->on_read (sub { }); $handle->on_eof (undef); $handle->on_error (sub { my $data = delete $_[0]{rbuf}; });
The reason to use on_error is that TCP connections, due to latencies and packets loss, might get closed quite violently with an error, when in fact, all data has been received.
It is usually better to use acknowledgements when transferring data, to make sure the other side hasn't just died and you got the data intact. This is also one reason why so many internet protocols have an explicit QUIT command.
After writing your last bits of data, set the on_drain callback and destroy the handle in there - with the default setting of low_water_mark this will be called precisely when all data has been written to the socket:
$handle->push_write (...); $handle->on_drain (sub { warn "all data submitted to the kernel\n"; undef $handle; });
If you just want to queue some data and then signal EOF to the other side, consider using ->push_shutdown instead.
->push_shutdown
If your TLS server is a pure TLS server (e.g. HTTPS) that only speaks TLS, simply connect to it and then create the AnyEvent::Handle with the tls parameter:
tcp_connect $host, $port, sub { my ($fh) = @_; my $handle = new AnyEvent::Handle fh => $fh, tls => "connect", on_error => sub { ... }; $handle->push_write (...); };
Then you should additionally enable certificate verification, including peername verification, if the protocol you use supports it (see AnyEvent::TLS, verify_peername).
E.g. for HTTPS:
tcp_connect $host, $port, sub { my ($fh) = @_; my $handle = new AnyEvent::Handle fh => $fh, peername => $host, tls => "connect", tls_ctx => { verify => 1, verify_peername => "https" }, ...
Note that you must specify the hostname you connected to (or whatever "peername" the protocol needs) as the peername argument, otherwise no peername verification will be done.
The above will use the system-dependent default set of trusted CA certificates. If you want to check against a specific CA, add the ca_file (or ca_cert) arguments to tls_ctx:
ca_file
ca_cert
tls_ctx
tls_ctx => { verify => 1, verify_peername => "https", ca_file => "my-ca-cert.pem", },
Well, you first need to get a server certificate and key. You have three options: a) ask a CA (buy one, use cacert.org etc.) b) create a self-signed certificate (cheap. check the search engine of your choice, there are many tutorials on the net) or c) make your own CA (tinyca2 is a nice program for that purpose).
Then create a file with your private key (in PEM format, see AnyEvent::TLS), followed by the certificate (also in PEM format). The file should then look like this:
-----BEGIN RSA PRIVATE KEY----- ...header data ... lots of base64'y-stuff -----END RSA PRIVATE KEY----- -----BEGIN CERTIFICATE----- ... lots of base64'y-stuff -----END CERTIFICATE-----
The important bits are the "PRIVATE KEY" and "CERTIFICATE" parts. Then specify this file as cert_file:
cert_file
tcp_server undef, $port, sub { my ($fh) = @_; my $handle = new AnyEvent::Handle fh => $fh, tls => "accept", tls_ctx => { cert_file => "my-server-keycert.pem" }, ...
When you have intermediate CA certificates that your clients might not know about, just append them to the cert_file.
In many cases, you might want to subclass AnyEvent::Handle.
To make this easier, a given version of AnyEvent::Handle uses these conventions:
all constructor arguments become object members.
At least initially, when you pass a tls-argument to the constructor it will end up in $handle->{tls}. Those members might be changed or mutated later on (for example tls will hold the TLS connection object).
other object member names are prefixed with an _.
_
All object members not explicitly documented (internal use) are prefixed with an underscore character, so the remaining non-_-namespace is free for use for subclasses.
all members not documented here and not prefixed with an underscore are free to use in subclasses.
Of course, new versions of AnyEvent::Handle may introduce more "public" member variables, but thats just life, at least it is documented.
Robin Redeker <elmex at ta-sa.org>, Marc Lehmann <schmorp@schmorp.de>.
<elmex at ta-sa.org>
To install AnyEvent, copy and paste the appropriate command in to your terminal.
cpanm
cpanm AnyEvent
CPAN shell
perl -MCPAN -e shell install AnyEvent
For more information on module installation, please visit the detailed CPAN module installation guide.