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# Wx::Connection

A Connection object represents the connection between a client
and a server. It is created by making a connection using a Client object, or by the acceptance of a
connection by a Server object. The
bulk of a DDE-like (Dynamic Data Exchange) conversation is
controlled by calling members in a Connection object or
by overriding its members. The actual DDE-based implementation
using DDEConnection is available on Windows only, but a
platform-independent, socket-based version of this API is
available using TCPConnection, which has the same API.

An application should normally derive a new connection class from
Connection, in order to override the communication event
handlers to do something interesting.

## Derived from

ConnectionBase

Object

## Types

IPCFormatIPCFormat is defined as follows:

enum IPCFormat { IPC_INVALID = 0, IPC_TEXT = 1, /* CF_TEXT */ IPC_BITMAP = 2, /* CF_BITMAP */ IPC_METAFILE = 3, /* CF_METAFILEPICT */ IPC_SYLK = 4, IPC_DIF = 5, IPC_TIFF = 6, IPC_OEMTEXT = 7, /* CF_OEMTEXT */ IPC_DIB = 8, /* CF_DIB */ IPC_PALETTE = 9, IPC_PENDATA = 10, IPC_RIFF = 11, IPC_WAVE = 12, IPC_UNICODETEXT = 13, IPC_ENHMETAFILE = 14, IPC_FILENAME = 15, /* CF_HDROP */ IPC_LOCALE = 16, IPC_PRIVATE = 20 };

## See also

Client, Server,
Interprocess communications overview

## Methods

- Connection.new
- Connection#advise
- Connection#execute
- Connection#disconnect
- Connection#on_advise
- Connection#on_disconnect
- Connection#on_execute
- Connection#on_poke
- Connection#on_request
- Connection#on_start_advise
- Connection#on_stop_advise
- Connection#poke
- Connection#request
- Connection#start_advise
- Connection#stop_advise

### Connection.new

Connection.new(%(arg-type)char% buffer, Integer size)

Constructs a connection object. If no user-defined connection
object is to be derived from Connection, then the constructor
should not be called directly, since the default connection
object will be provided on requesting (or accepting) a
connection. However, if the user defines his or her own derived
connection object, the Server#on_accept_connection and/or Client#on_make_connection
members should be replaced by functions which construct the new
connection object.

If the arguments of the Connection constructor are void then
the Connection object manages its own connection buffer,
allocating memory as needed. A programmer-supplied buffer cannot
be increased if necessary, and the program will assert if it is
not large enough. The programmer-supplied buffer is included
mainly for backwards compatibility.

### Connection#advise

Boolean advise(%(arg-type)String% item, char data, Integer size = -1, IPCFormat format = CF_TEXT)

Called by the server application to advise the client of a change
in the data associated with the given item. Causes the client
connection’s Connection#on_advise member
to be called. Returns true if successful.

### Connection#execute

Boolean execute(%(arg-type)char% data, Integer size = -1, IPCFormat format = CF_TEXT)

Called by the client application to execute a command on the
server. Can also be used to transfer arbitrary data to the server
(similar to Connection#poke in
that respect). Causes the server connection’s Connection#on_execute
member to be called. Returns true if successful.

### Connection#disconnect

Boolean disconnect()

Called by the client or server application to disconnect from the
other program; it causes the Connection#on_disconnect
message to be sent to the corresponding connection object in the
other program. Returns true if successful or already disconnected.
The application that calls Disconnect must explicitly delete
its side of the connection.

### Connection#on_advise

Boolean on_advise(%(arg-type)String% topic, String item, char data, Integer size, IPCFormat format)

Message sent to the client application when the server notifies
it of a change in the data associated with the given item, using
Advise.

### Connection#on_disconnect

Boolean on_disconnect()

Message sent to the client or server application when the other
application notifies it to end the connection. The default
behaviour is to delete the connection object and return true, so
applications should generally override OnDisconnect
(finally calling the inherited method as well) so that they know
the connection object is no longer available.

### Connection#on_execute

Boolean on_execute(%(arg-type)String% topic, char data, Integer size, IPCFormat format)

Message sent to the server application when the client notifies
it to execute the given data, using Execute.
Note that there is no item associated with this message.

### Connection#on_poke

Boolean on_poke(%(arg-type)String% topic, String item, char data, Integer size, IPCFormat format)

Message sent to the server application when the client notifies it to
accept the given data.

### Connection#on_request

char on_request(%(arg-type)String% topic, String item, Integer size, IPCFormat format)

Message sent to the server application when the client calls
Connection#request. The
server’s on_request method
should respond by returning a character string, or NULL to
indicate no data, and setting *size. The character string must of
course persist after the call returns.

### Connection#on_start_advise

Boolean on_start_advise(%(arg-type)String% topic, String item)

Message sent to the server application by the client, when the client
wishes to start an `advise loop’ for the given topic and item. The
server can refuse to participate by returning false.

### Connection#on_stop_advise

Boolean on_stop_advise(%(arg-type)String% topic, String item)

Message sent to the server application by the client, when the client
wishes to stop an `advise loop’ for the given topic and item. The
server can refuse to stop the advise loop by returning false, although
this doesn’t have much meaning in practice.

### Connection#poke

Boolean poke(%(arg-type)String% item, char data, Integer size = -1, IPCFormat format = CF_TEXT)

Called by the client application to poke data into the server.
Can be used to transfer arbitrary data to the server. Causes the
server connection’s Connection#on_poke member to
be called. If size is -1 the size is computed from the string
length of data.

Returns true if successful.

### Connection#request

char request(%(arg-type)String% item, Integer size, IPCFormat format = IPC_TEXT)

Called by the client application to request data from the server.
Causes the server connection’s Connection#on_request
member to be called. Size may be NULL or a pointer to a variable
to receive the size of the requested item.

Returns a character string (actually a pointer to the
connection’s buffer) if successful, NULL otherwise. This buffer
does not need to be deleted.

### Connection#start_advise

Boolean start_advise(%(arg-type)String% item)

Called by the client application to ask if an advise loop can be
started with the server. Causes the server connection’s
Connection#on_start_advise member to be called. Returns true if the server okays it, false
otherwise.

### Connection#stop_advise

Boolean stop_advise(%(arg-type)String% item)

Called by the client application to ask if an advise loop can be
stopped. Causes the server connection’s Connection#on_stop_advise
member to be called. Returns true if the server okays it, false
otherwise.

[This page automatically generated from the Textile source at 2023-06-09 00:45:24 +0000]