POE::Component::Server::TCP - a simplified TCP server


POE::Component::Server::TCP - a simplified TCP server


  use POE qw(Component::Server::TCP);
  ### First form just accepts connections.
  my $acceptor_session_id = POE::Component::Server::TCP->new(
    Port     => $bind_port,
    Address  => $bind_address,    # Optional.
    Hostname => $bind_hostname,   # Optional.
    Domain   => AF_INET,          # Optional.
    Alias    => $session_alias,   # Optional.
    Acceptor => \&accept_handler,
    Error    => \&error_handler,  # Optional.
  ### Second form also handles connections.
  my $acceptor_session_id = POE::Component::Server::TCP->new(
    Port     => $bind_port,
    Address  => $bind_address,      # Optional.
    Hostname => $bind_hostname,     # Optional.
    Domain   => AF_INET,            # Optional.
    Alias    => $session_alias,     # Optional.
    Error    => \&error_handler,    # Optional.
    Args     => [ "arg0", "arg1" ], # Optional.
    Concurrency => -1,              # Optional.
    SessionType   => "POE::Session::Abc",           # Optional.
    SessionParams => [ options => { debug => 1 } ], # Optional.
    ClientInput        => \&handle_client_input,      # Required.
    ClientConnected    => \&handle_client_connect,    # Optional.
    ClientDisconnected => \&handle_client_disconnect, # Optional.
    ClientError        => \&handle_client_error,      # Optional.
    ClientFlushed      => \&handle_client_flush,      # Optional.
    ClientFilter       => POE::Filter::Xyz->new()",   # Optional.
    ClientInputFilter  => POE::Filter::Xyz->new(),    # Optional.
    ClientOutputFilter => POE::Filter::Xyz->new(),    # Optional.
    ClientShutdownOnError => 0,                       # Optional.
    # Optionally define other states for the client session.
    InlineStates  => { ... },
    PackageStates => [ ... ],
    ObjectStates  => [ ... ],
  ### Call signatures for handlers.
  sub accept_handler {
    my ($socket, $remote_address, $remote_port) = @_[ARG0, ARG1, ARG2];
  sub error_handler {
    my ($syscall_name, $error_number, $error_string) = @_[ARG0, ARG1, ARG2];
  sub handle_client_input {
    my $input_record = $_[ARG0];
  sub handle_client_error {
    my ($syscall_name, $error_number, $error_string) = @_[ARG0, ARG1, ARG2];
  sub handle_client_connect {
    # no special parameters
  sub handle_client_disconnect {
    # no special parameters
  sub handle_client_flush {
    # no special parameters
  ### Reserved HEAP variables:
  $heap->{listener}    = SocketFactory (only Acceptor and Error callbacks)
  $heap->{client}      = ReadWrite     (only in ClientXyz callbacks)
  $heap->{remote_ip}   = remote IP address in dotted form
  $heap->{remote_port} = remote port
  $heap->{remote_addr} = packed remote address and port
  $heap->{shutdown}    = shutdown flag (check to see if shutting down)
  $heap->{shutdown_on_error} = Automatically disconnect on error.
  ### Accepted public events.
  # Start shutting down this connection.
  $kernel->yield( "shutdown" );
  # Stop listening for connections.
  $kernel->post( server => "shutdown" );
  # Set the maximum number of simultaneous connections.
  $kernel->call( server => set_concurrency => $count );
  ### Responding to a client.


The TCP server component hides a generic TCP server pattern. It uses POE::Wheel::SocketFactory and POE::Wheel::ReadWrite internally, creating a new session for each connection to arrive.

The authors hope that generic servers can be created with as little work as possible. Servers with uncommon requirements may need to be written using the wheel classes directly. That isn't terribly difficult. A tutorial at http://poe.perl.org/ describes how.


The new() method can accept quite a lot of parameters. It will return the session ID of the accecptor session. One must use callbacks to check for errors rather than the return value of new().

POE::Component::Server::TCP supplies common defaults for most callbacks and handlers.

Acceptor => CODEREF
Acceptor sets a mostly obsolete callback that is expected to create the connection sessions manually. Most programs should use the /^Client/ callbacks instead.

The coderef receives its parameters directly from SocketFactory's SuccessEvent. ARG0 is the accepted socket handle, suitable for giving to a ReadWrite wheel. ARG1 and ARG2 contain the packed remote address and numeric port, respectively. ARG3 is the SocketFactory wheel's ID.

  Acceptor => \&accept_handler

Acceptor lets programmers rewrite the guts of Server::TCP entirely. It is not compatible with the /^Client/ callbacks.

Address => SCALAR
Address is the optional interface address the TCP server will bind to. It defaults to INADDR_ANY or INADDR6_ANY when using IPv4 or IPv6, respectively.
  Address => ''   # Localhost IPv4
  Address => "::1"         # Localhost IPv6

It's passed directly to SocketFactory's BindAddress parameter, so it can be in whatever form SocketFactory supports. At the time of this writing, that's a dotted quad, an IPv6 address, a host name, or a packed Internet address. See also the Hostname parameter.

Alias => SCALAR
Alias is an optional name by which the server's listening session will be known. Messages sent to the alias will go to the listening session, not the sessions that are handling active connections.
  Alias => 'chargen'

Later on, the 'chargen' service can be shut down with:

  $kernel->post( chargen => 'shutdown' );

Args passes the ARRAYREF to the ClientConnected callback as ARG0. It allows you to send extra information to the sessions that handle each client connection.

ClientConnected => CODEREF
ClientConnected sets the callback used to notify each new client session that it is started. ClientConnected callbacks receive the usual POE parameters, plus a copy of whatever was specified in the component's Args constructor parameter, as ARG0.

The ClientConnected callback will not be called within the same session context twice.

ClientDisconnected => CODEREF
ClientDisconnected sets the callback used to notify a client session that the client has disconnected.

ClientDisconnected callbacks receive the usual POE parameters, but nothing special is included.

ClientError => CODEREF
ClientError sets the callback used to notify a client session that there has been an error on the connection.

It receives POE's usual error handler parameters: ARG0 is the name of the function that failed. ARG1 is the numeric failure code ($! in numeric context). ARG2 is the string failure code ($! in string context), and so on.

POE::Wheel::ReadWrite discusses the error parameters in more detail.

A default error handler will be provided if ClientError is omitted. The default handler will log most errors to STDERR.

The value of ClientShutdownOnError determines whether the connection will be shutdown after errors are received. It is the client shutdown, not the error, that invokes ClientDisconnected callbacks.

ClientFilter => SCALAR
ClientFilter => ARRAYREF
ClientFilter => OBJECT
ClientFilter specifies the type of filter that will parse input from each client, and optionally any constructor arguments used to create each filter instance.

It can take a class name, an arrayref, or a POE::Filter object.

If ClientFilter contains a SCALAR, it defines the name of the POE::Filter class. Default constructor parameters will be used to create instances of that filter.

  ClientFilter => "POE::Filter::Stream",

If ClientFilter contains a list reference, the first item in the list will be a POE::Filter class name, and the remaining items will be constructor parameters for the filter. For example, this changes the line separator to a vertical bar:

  ClientFilter => [ "POE::Filter::Line", Literal => "|" ],

If ClientFilter contains an object, it will have a clone method called on it each time a client connects.

  ClientFilter => POE::Filter::Block->new()

ClientFilter is optional. The component will use ``POE::Filter::Line'' if it is omitted.

If you supply a different value for Filter, then you must also use that filter class.

ClientInputFilter => SCALAR
ClientInputFilter => ARRAYREF
ClientInputFilter => OBJECT
ClientOutputFilter => SCALAR
ClientOutputFilter => ARRAYREF
ClientOutputFilter => OBJECT
ClientInputFilter and ClientOutputFilter act like ClientFilter, but they allow programs to specify different filters for input and output. Both must be used together.

Usage is the same as ClientFilter.

  ClientInputFilter  => [ "POE::Filter::Line", Literal => "|" ],
  ClientOutputFilter => "POE::Filter::Stream",
  ClientInputFilter  => POE::Filter::Block->new(),

ClientInput => CODEREF
ClientInput sets a callback that will be called to handle client input. The callback receives its parameters directly from ReadWrite's InputEvent. ARG0 is the input record, and ARG1 is the wheel's unique ID, and so on. POE::Wheel::ReadWrite discusses input event handlers in more detail.
  ClientInput => \&input_handler

ClientInput and Acceptor are mutually exclusive. Enabling one prohibits the other.

ClientShutdownOnError => BOOLEAN
ClientShutdownOnError tells the component whether to shut down client sessions automatically on errors. It defaults to true. Setting it to a false value (0, undef, ``'') turns this feature off.

If this option is turned off, it becomes your responsibility to deal with client errors properly. Not handling them, or not destroying wheels when they should be, will cause the component to spit out a constant stream of errors, eventually bogging down your application with dead connections that spin out of control.

You've been warned.

Domain => SCALAR
Specifies the domain within which communication will take place. It selects the protocol family which should be used. Currently supported values are AF_INET, AF_INET6, PF_INET or PF_INET6. This parameter is optional and will default to AF_INET if omitted.

Note: AF_INET6 and PF_INET6 are supplied by the Socket6 module, which is available on the CPAN. You must have Socket6 loaded before POE::Component::Server::TCP will create IPv6 sockets.

Error => CODEREF
Error sets the callback that will be invoked when the server socket reports an error. The callback is used to handle POE::Wheel::SocketFactory's FailureEvent, so it receives the same parameters as discussed there.

A default error handler will be provided if Error is omitted. The default handler will log the error to STDERR and shut down the server. Active connections will have the opportunity to complete their transactions.

Hostname => SCALAR
Hostname is the optional non-packed name of the interface the TCP server will bind to. This will always be converted via inet_aton and so can either be a dotted quad or a name. If you know that you are passing in text, then this parameter should be used in preference to Address, to prevent confusion in the case that the hostname happens to be 4 bytes in length. In the case that both are provided, then the Address parameter overrides the Hostname parameter.

InlineStates => HASHREF
InlineStates holds a hashref of callbacks to handle custom events. The hashref follows the same form as POE::Session->create()'s inline_states parameter.

ObjectStates => ARRAYREF
ObjectStates holds a list reference of objects and the events they handle. The ARRAYREF follows the same form as POE::Session->create()'s object_states parameter.

PackageStates => ARRAYREF
PackageStates holds a list reference of Perl package names and the events they handle. The ARRAYREF follows the same form as POE::Session->create()'s package_states parameter.

Port => SCALAR
Port contains the port the listening socket will be bound to. It defaults to INADDR_ANY, which usually lets the operating system pick a port at random.
  Port => 30023

SessionParams => ARRAYREF
SessionParams specifies additional parameters that will be passed to the SessionType constructor at creation time. It must be an array reference.
  SessionParams => [ options => { debug => 1, trace => 1 } ],

It is important to realize that some of the arguments to SessionHandler may get clobbered when defining them for your SessionHandler. It is advised that you stick to defining arguments in the ``options'' hash such as trace and debug. See the POE::Session manpage for an example list of options.

SessionType => SCALAR
SessionType specifies what type of sessions will be created within the TCP server. It must be a scalar value.
  SessionType => "POE::Session::MultiDispatch"

SessionType is optional. The component will create POE::Session instances if a new type isn't specified.

Started => CODEREF
Started sets a callback that will be invoked within the main server session's context. It notifies your code that the server has started. Its parameters are the usual for a session's _start handler.

Started is optional.

Concurrency => SCALAR
Controls the number of connections that may be open at the same time. Defaults to -1, which means unlimited number of simutaneous connections. 0 means no connections. This value may be set via the set_concurrency event, see EVENTS.

Note that if you define the Acceptor callback, you will have to inform the TCP server session that a connection was closed. This is done by sending a disconnected event to your session's parent. This is only necessary if you define an Acceptor callback. For ClientInput, it's all handled for you.


  Acceptor => sub {
    # ....
      # ....
      inline_states => {
        _start => sub {
          # ....
          # remember who our parent is
          $_[HEAP]->{server_tcp} = $_[SENDER]->ID;
          # ....
        got_client_disconnect => sub {
          # ....
          $_[KERNEL]->post( $_[HEAP]->{server_tcp} => 'disconnected' );
          # ....


It's possible to manipulate a TCP server component by sending it messages.

Shuts down the TCP server. This entails destroying the SocketFactory that's listening for connections and removing the TCP server's alias, if one is set.

Active connections are not shut down until they disconnect.

Inform the TCP server that a connection was closed. This is only necessary when using Concurrency is set and you are using an Acceptor callback.

Set the number of simultaneous connections. See Concurrency above.
  $kernel->call( "tcp_server_alias", "set_concurrency", $max_count );


POE::Component::Client::TCP, POE::Wheel::SocketFactory, POE::Wheel::ReadWrite, POE::Filter


This looks nothing like what Ann envisioned.

This component currently does not accept many of the options that POE::Wheel::SocketFactory does.

This component will not bind to several addresses at once. This may be a limitation in SocketFactory, but it's not by design.

This component needs more complex error handling which appends for construction errors and replaces for runtime errors, instead of replacing for all.

Some use cases require different session classes for the listener and the connection handlers. This isn't currently supported. Please send patches. :)


POE::Component::Server::TCP is Copyright 2000-2006 by Rocco Caputo. All rights are reserved. POE::Component::Server::TCP is free software, and it may be redistributed and/or modified under the same terms as Perl itself.

POE::Component::Server::TCP is based on code, used with permission, from Ann Barcomb <kudra@domaintje.com>.

POE::Component::Server::TCP is based on code, used with permission, from Jos Boumans <kane@cpan.org>.

 POE::Component::Server::TCP - a simplified TCP server