36c9828f70
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@51911 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
225 lines
8.9 KiB
C++
225 lines
8.9 KiB
C++
/////////////////////////////////////////////////////////////////////////////
|
|
// Name: ipc
|
|
// Purpose: topic overview
|
|
// Author: wxWidgets team
|
|
// RCS-ID: $Id$
|
|
// Licence: wxWindows license
|
|
/////////////////////////////////////////////////////////////////////////////
|
|
|
|
/*!
|
|
|
|
@page ipc_overview Interprocess communication overview
|
|
|
|
Classes: #wxServer,
|
|
#wxConnection,
|
|
#wxClient
|
|
wxWidgets has a number of different classes to help with
|
|
interprocess communication and network programming. This section
|
|
only discusses one family of classes -- the DDE-like protocol --
|
|
but here's a list of other useful classes:
|
|
|
|
|
|
#wxSocketEvent,
|
|
#wxSocketBase,
|
|
#wxSocketClient,
|
|
#wxSocketServer: classes for the low-level TCP/IP API.
|
|
#wxProtocol, #wxURL, #wxFTP, #wxHTTP: classes
|
|
for programming popular Internet protocols.
|
|
|
|
|
|
wxWidgets' DDE-like protocol is a high-level protocol based on
|
|
Windows DDE. There are two implementations of this DDE-like
|
|
protocol: one using real DDE running on Windows only, and another
|
|
using TCP/IP (sockets) that runs on most platforms. Since the API
|
|
and virtually all of the behaviour is the same apart from the
|
|
names of the classes, you should find it easy to switch between
|
|
the two implementations.
|
|
Notice that by including @c wx/ipc.h you may define
|
|
convenient synonyms for the IPC classes: @c wxServer for either
|
|
@c wxDDEServer or @c wxTCPServer depending on whether
|
|
DDE-based or socket-based implementation is used and the same
|
|
thing for @c wxClient and @c wxConnection.
|
|
By default, the DDE implementation is used under Windows. DDE works
|
|
within one computer only. If you want to use IPC between
|
|
different workstations you should define @c wxUSE_DDE_FOR_IPC as 0 before including this header -- this
|
|
will force using TCP/IP implementation even under Windows.
|
|
The following description refers to wx... but remember that the
|
|
equivalent wxTCP... and wxDDE... classes can be used in much the
|
|
same way.
|
|
Three classes are central to the DDE-like API:
|
|
|
|
|
|
wxClient. This represents the client application, and is used
|
|
only within a client program.
|
|
wxServer. This represents the server application, and is used
|
|
only within a server program.
|
|
wxConnection. This represents the connection from the
|
|
client to the server - both the client and the server use an
|
|
instance of this class, one per connection. Most DDE transactions
|
|
operate on this object.
|
|
|
|
|
|
Messages between applications are usually identified by three
|
|
variables: connection object, topic name and item name. A data
|
|
string is a fourth element of some messages. To create a
|
|
connection (a conversation in Windows parlance), the client
|
|
application uses wxClient::MakeConnection to send a message to the
|
|
server object, with a string service name to identify the server
|
|
and a topic name to identify the topic for the duration of the
|
|
connection. Under Unix, the service name may be either an integer
|
|
port identifier in which case an Internet domain socket will be
|
|
used for the communications or a valid file name (which shouldn't
|
|
exist and will be deleted afterwards) in which case a Unix domain
|
|
socket is created.
|
|
@b SECURITY NOTE: Using Internet domain sockets is extremely insecure for
|
|
IPC as there is absolutely no access control for them, use Unix domain sockets
|
|
whenever possible!
|
|
The server then responds and either vetoes the connection or
|
|
allows it. If allowed, both the server and client objects create
|
|
wxConnection objects which persist until the connection is
|
|
closed. The connection object is then used for sending and
|
|
receiving subsequent messages between client and server -
|
|
overriding virtual functions in your class derived from
|
|
wxConnection allows you to handle the DDE messages.
|
|
To create a working server, the programmer must:
|
|
|
|
|
|
Derive a class from wxConnection, providing handlers for various messages sent to the server
|
|
side of a wxConnection (e.g. OnExecute, OnRequest, OnPoke). Only
|
|
the handlers actually required by the application need to be
|
|
overridden.
|
|
Derive a class from wxServer, overriding OnAcceptConnection
|
|
to accept or reject a connection on the basis of the topic
|
|
argument. This member must create and return an instance of the
|
|
derived connection class if the connection is accepted.
|
|
Create an instance of your server object and call Create to
|
|
activate it, giving it a service name.
|
|
|
|
|
|
To create a working client, the programmer must:
|
|
|
|
|
|
Derive a class from wxConnection, providing handlers for various
|
|
messages sent to the client side of a wxConnection (e.g.
|
|
OnAdvise). Only the handlers actually required by the application
|
|
need to be overridden.
|
|
Derive a class from wxClient, overriding OnMakeConnection to
|
|
create and return an instance of the derived connection class.
|
|
Create an instance of your client object.
|
|
When appropriate, create a new connection using
|
|
wxClient::MakeConnection,
|
|
with arguments host name (processed in Unix only, use 'localhost'
|
|
for local computer), service name, and topic name for this
|
|
connection. The client object will call
|
|
#OnMakeConnection to create
|
|
a connection object of the derived class if the connection is
|
|
successful.
|
|
Use the wxConnection member functions to send messages to the server.
|
|
|
|
|
|
@ref datatransfer_overview
|
|
#Examples
|
|
@ref ddedetails_overview
|
|
|
|
|
|
@section datatransfer Data transfer
|
|
|
|
These are the ways that data can be transferred from one
|
|
application to another. These are methods of wxConnection.
|
|
|
|
|
|
@b Execute: the client calls the server with a data string representing
|
|
a command to be executed. This succeeds or fails, depending on the
|
|
server's willingness to answer. If the client wants to find the result
|
|
of the Execute command other than success or failure, it has to explicitly
|
|
call Request.
|
|
@b Request: the client asks the server for a particular data string
|
|
associated with a given item string. If the server is unwilling to
|
|
reply, the return value is @NULL. Otherwise, the return value is a string
|
|
(actually a pointer to the connection buffer, so it should not be
|
|
deallocated by the application).
|
|
@b Poke: The client sends a data string associated with an item
|
|
string directly to the server. This succeeds or fails.
|
|
@b Advise: The client asks to be advised of any change in data
|
|
associated with a particular item. If the server agrees, the server will
|
|
send an OnAdvise message to the client along with the item and data.
|
|
|
|
|
|
The default data type is wxCF_TEXT (ASCII text), and the default data
|
|
size is the length of the null-terminated string. Windows-specific data
|
|
types could also be used on the PC.
|
|
|
|
@section ipcexamples Examples
|
|
|
|
See the sample programs @e server and @e client in the IPC
|
|
samples directory. Run the server, then the client. This demonstrates
|
|
using the Execute, Request, and Poke commands from the client, together
|
|
with an Advise loop: selecting an item in the server list box causes
|
|
that item to be highlighted in the client list box.
|
|
|
|
@section ddedetails More DDE details
|
|
|
|
A wxClient object initiates the client part of a client-server
|
|
DDE-like (Dynamic Data Exchange) conversation (available in both
|
|
Windows and Unix).
|
|
To create a client which can communicate with a suitable server,
|
|
you need to derive a class from wxConnection and another from
|
|
wxClient. The custom wxConnection class will receive
|
|
communications in a 'conversation' with a server. and the custom
|
|
wxServer is required so that a user-overridden
|
|
wxClient::OnMakeConnection
|
|
member can return a wxConnection of the required class, when a
|
|
connection is made.
|
|
For example:
|
|
|
|
@code
|
|
class MyConnection: public wxConnection {
|
|
public:
|
|
MyConnection(void)::wxConnection() {}
|
|
~MyConnection(void) { }
|
|
bool OnAdvise(const wxString& topic, const wxString& item, char *data, int size, wxIPCFormat format)
|
|
{ wxMessageBox(topic, data); }
|
|
};
|
|
|
|
class MyClient: public wxClient {
|
|
public:
|
|
MyClient(void) {}
|
|
wxConnectionBase *OnMakeConnection(void) { return new MyConnection; }
|
|
};
|
|
@endcode
|
|
|
|
Here, @b MyConnection will respond to
|
|
#OnAdvise messages sent by the
|
|
server by displaying a message box.
|
|
When the client application starts, it must create an instance of
|
|
the derived wxClient. In the following, command line arguments
|
|
are used to pass the host name (the name of the machine the
|
|
server is running on) and the server name (identifying the server
|
|
process). Calling
|
|
wxClient::MakeConnection
|
|
implicitly creates an instance of @b MyConnection if the
|
|
request for a connection is accepted, and the client then
|
|
requests an @e Advise loop from the server (an Advise loop is
|
|
where the server calls the client when data has changed).
|
|
|
|
@code
|
|
wxString server = "4242";
|
|
wxString hostName;
|
|
wxGetHostName(hostName);
|
|
|
|
// Create a new client
|
|
MyClient *client = new MyClient;
|
|
connection = (MyConnection *)client-MakeConnection(hostName, server, "IPC TEST");
|
|
|
|
if (!connection)
|
|
{
|
|
wxMessageBox("Failed to make connection to server", "Client Demo Error");
|
|
return @NULL;
|
|
}
|
|
connection-StartAdvise("Item");
|
|
@endcode
|
|
|
|
*/
|
|
|
|
|