PipeServer Component

Properties   Methods   Events   Config Settings   Errors  

The PipeServer component is a lightweight server component based on an asynchronous, event-driven architecture. It is designed to balance the load between connections for a fast, powerful server.

Syntax

TiipPipeServer

Remarks

PipeServer is the server complement of PipeClient (which is used to create client applications). They share a common design philosophy and interface. PipeServer is as easy to use as PipeClient.

The client connections are identified by a ConnectionId, an id generated by the component to identify each connection. This id is unique to each connection. PipeServer's events also have ConnectionId as a parameter to identify the connection to which they are related.

Our main goal in designing PipeServer was to make it easy to use without sacrificing performance. The component has a minimum of properties, and events: Connected, DataIn, Disconnected, ReadyToSend, and Error.

PipeServer can start to listen on a pipe by setting PipeName and then setting Listening to True. When a client connects the Connected event fires, a ConnectionId is assigned, and communication can start. From this point on, the operation is very similar to PipeClient. Data is sent by assigning the data string to the DataToSend property.

Property List

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The following is the full list of the properties of the component with short descriptions. Click on the links for further details.

Method List

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The following is the full list of the methods of the component with short descriptions. Click on the links for further details.

Event List

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The following is the full list of the events fired by the component with short descriptions. Click on the links for further details.

Config Settings

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The following is a list of config settings for the component with short descriptions. Click on the links for further details.

Connections Property (PipeServer Component)

A collection of currently connected clients.

Syntax

property Connections: TiipPipeConnectionList read get_Connections;

Remarks

This property contains a collection of currently connected clients. All of the connections may be managed using this property. Each connection is described by the different fields of the PipeConnection type.

This collection is a hashtable type of collection, in which the Connection Id string is used as the key to the desired connection. The Connected event fires when a client connects and provides the Connection Id (key) that identifies the client.

Example (Broadcasting Data) For i = 0 to Control.ConnectionCount Control.DataToSend(Control.ConnectionId(i)) = "Broadcast Data" Next i

This property is read-only.

Please refer to the PipeConnection type for a complete list of fields.

DefaultEOL Property (PipeServer Component)

This property includes a default end-of-line (EOL) value to be used by incoming connections.

Syntax

property DefaultEOL: String read get_DefaultEOL write set_DefaultEOL;
property DefaultEOLB: TBytes read get_DefaultEOLB write set_DefaultEOLB;

Default Value

''

Remarks

This property contains a default end-of-line (EOL) value to be used by incoming connections. Once the component accepts and establishes an inbound connection, it will set that connection's EOL to the value in this property. By default, this value is empty (""), meaning that data will be fired as it is received.

DefaultMaxLineLength Property (PipeServer Component)

The property includes the default maximum line length value for inbound connections.

Syntax

property DefaultMaxLineLength: Integer read get_DefaultMaxLineLength write set_DefaultMaxLineLength;

Default Value

2048

Remarks

This property controls the default size of an internal buffer that holds received data while waiting for an end-of-line (EOL) string.

The minimum value for this property is 256 bytes. The default value is 2048 bytes.

DefaultSingleLineMode Property (PipeServer Component)

This property tells the component whether or not to treat new connections as line oriented.

Syntax

property DefaultSingleLineMode: Boolean read get_DefaultSingleLineMode write set_DefaultSingleLineMode;

Default Value

false

Remarks

This property instructs the component whether or not to treat newly established connections as line-oriented protocols. If this value is True, newly accepted connections will read the incoming data stream as lines separated by a carriage return line feed (CRLF), carriage return (CR), or line feed (LF) and will ignore the end of lines (EOLs).

DefaultTimeout Property (PipeServer Component)

This property includes an initial timeout value to be used by incoming connections.

Syntax

property DefaultTimeout: Integer read get_DefaultTimeout write set_DefaultTimeout;

Default Value

0

Remarks

This property is used by the component to set the operational timeout value of all inbound connections once they are established.

By default, the timeout is 0, meaning that all inbound connections will behave asynchronously.

Listening Property (PipeServer Component)

If True, the component accepts incoming connections.

Syntax

property Listening: Boolean read get_Listening write set_Listening;

Default Value

false

Remarks

Use this property to make the component 'listen' (accept connections) on the pipe specified by PipeName. Setting this property to False will make the component stop listening. Please note that this does not close any existing connections.

Note: Use the StartListening and StopListening methods to control whether the component is listening.

This property is not available at design time.

PipeName Property (PipeServer Component)

The name of the pipe.

Syntax

property PipeName: String read get_PipeName write set_PipeName;

Default Value

''

Remarks

This property specifies the name of the pipe on which to accept connections. Clients must use this name when establishing a connection to PipeServer.

Config Method (PipeServer Component)

Sets or retrieves a configuration setting.

Syntax

function Config(ConfigurationString: String): String;

Remarks

Config is a generic method available in every component. It is used to set and retrieve configuration settings for the component.

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the component, access to these internal properties is provided through the Config method.

To set a configuration setting named PROPERTY, you must call Config("PROPERTY=VALUE"), where VALUE is the value of the setting expressed as a string. For boolean values, use the strings "True", "False", "0", "1", "Yes", or "No" (case does not matter).

To read (query) the value of a configuration setting, you must call Config("PROPERTY"). The value will be returned as a string.

Disconnect Method (PipeServer Component)

This method disconnects the specified client.

Syntax

procedure Disconnect(ConnectionId: Integer);

Remarks

Calling this method will disconnect the client specified by the ConnectionId parameter.

DoEvents Method (PipeServer Component)

Processes events from the internal message queue.

Syntax

procedure DoEvents();

Remarks

When DoEvents is called, the component processes any available events. If no events are available, it waits for a preset period of time, and then returns.

Interrupt Method (PipeServer Component)

This method interrupts a synchronous send to the remote host.

Syntax

procedure Interrupt(ConnectionId: Integer);

Remarks

This property is called using the Connection Id if you wish to interrupt a connection and stop a file from uploading without disconnecting the client connected to the component. If you use SendFile to upload a file, the component will run synchronously on that Connection Id until it is completed.

Send Method (PipeServer Component)

This method sends binary data to the specified client.

Syntax

procedure Send(ConnectionId: Integer; Text: TBytes);

Remarks

This method sends binary data to the client identified by ConnectionId. To send text, use the SendText method instead.

When Timeout is set to 0, the component will behave asynchronously. If you are sending data to the remote host faster than it can process it, or faster than the network's bandwidth allows, the outgoing queue might fill up. When this happens, the operation raises the exception with errorcode 10035 and message '[10035] Operation would block' (WSAEWOULDBLOCK). You can handle this exception, and then try to send the data again. . The BytesSent property shows how many bytes were sent (if any). If 0 bytes were sent, then you can wait for the ReadyToSend event before attempting to send data again.

Note: The ReadyToSend event is not fired when part of the data is sent successfully.

SendFile Method (PipeServer Component)

This method sends the file to the remote host.

Syntax

procedure SendFile(ConnectionId: Integer; FileName: String);

Remarks

This method sends the file to the client specified by the ConnectionId.

SendLine Method (PipeServer Component)

This method sends a string followed by a new line.

Syntax

procedure SendLine(ConnectionId: Integer; Text: String);

Remarks

This method is used to send data with line-oriented protocols. The line is followed by CRLF ('#13#10') .

Please refer to the GetLine method and SingleLineMode property for more information.

Shutdown Method (PipeServer Component)

This method shuts down the server.

Syntax

procedure Shutdown();

Remarks

This method shuts down the server. Calling this method is equivalent to calling StopListening and then breaking every client connection by calling Disconnect.

StartListening Method (PipeServer Component)

This method starts listening for incoming connections.

Syntax

procedure StartListening();

Remarks

This method begins listening for incoming connections on the pipe specified by PipeName.

To stop listening for new connections, call StopListening. To stop listening for new connections and to disconnect all existing clients, call Shutdown.

StopListening Method (PipeServer Component)

This method stops listening for new connections.

Syntax

procedure StopListening();

Remarks

This method stops listening for new connections. After being called, any new connection attempts will be rejected. Calling this method does not disconnect existing connections.

To stop listening and to disconnect all existing clients, call Shutdown instead.

Connected Event (PipeServer Component)

Fired immediately after a connection completes.

Syntax

type TConnectedEvent = procedure (
  Sender: TObject;
  ConnectionId: Integer
) of Object;

property OnConnected: TConnectedEvent read FOnConnected write FOnConnected;

Remarks

This event fires immediately after a client connects. The ConnectionId parameter identifies the client connection.

DataIn Event (PipeServer Component)

This event is fired when data come in.

Syntax

type TDataInEvent = procedure (
  Sender: TObject;
  ConnectionId: Integer;
  Text: String;
  TextB: TBytes;
  EOL: Boolean
) of Object;

property OnDataIn: TDataInEvent read FOnDataIn write FOnDataIn;

Remarks

Trapping the DataIn event is your only chance to get the data coming from the other end of the connection specified by ConnectionId. The incoming data are provided through the Text parameter.

EOL indicates whether or not the EOL string was found at the end of Text. If the EOL string was found, then EOL is True.

If Text is part of the data portion of length larger than either DefaultMaxLineLength or MaxLineLength with no EOL strings in it, then EOL is False. Please note that this means that one or more DataIn events with EOL set to False can be received during a connection.

If the EOL property is '' (empty string), then EOL can be disregarded (it is always True).

Note: Events are not re-entrant. Performing time-consuming operations within this event will prevent it from firing again in a timely manner and may affect overall performance.

Disconnected Event (PipeServer Component)

Fires when a client disconnects.

Syntax

type TDisconnectedEvent = procedure (
  Sender: TObject;
  ConnectionId: Integer
) of Object;

property OnDisconnected: TDisconnectedEvent read FOnDisconnected write FOnDisconnected;

Remarks

This event fires when a client disconnects. The ConnectionId parameters identifies the client that is disconnected.

Error Event (PipeServer Component)

This event fires information about errors during data delivery.

Syntax

type TErrorEvent = procedure (
  Sender: TObject;
  ConnectionId: Integer;
  ErrorCode: Integer;
  const Description: String
) of Object;

property OnError: TErrorEvent read FOnError write FOnError;

Remarks

The Error event is fired in case of exceptional conditions during message processing. Normally, the component raises an exception.

ErrorCode contains an error code and Description contains a textual description of the error. For a list of valid error codes and their descriptions, please refer to the Error Codes section.

ConnectionId indicates the connection for which the error is applicable.

ReadyToSend Event (PipeServer Component)

Fired when the component is ready to send data.

Syntax

type TReadyToSendEvent = procedure (
  Sender: TObject;
  ConnectionId: Integer
) of Object;

property OnReadyToSend: TReadyToSendEvent read FOnReadyToSend write FOnReadyToSend;

Remarks

The ReadyToSend event indicates that the underlying pipe is ready to accept data after a failed DataToSend. The event is also fired immediately after a connection to the remote host is established.

PipeConnection Type

A currently connected client.

Remarks

This type describes the connection of a client which is currently connected to the component. The connection may be managed using the different fields of this type.

Fields

Constructors

constructor Create();

Config Settings (PipeServer Component)

The component accepts one or more of the following configuration settings. Configuration settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the component, access to these internal properties is provided through the Config method.

PipeServer Config Settings

Base Config Settings

Trappable Errors (PipeServer Component)

PipeServer Errors

	401   Failed to create event.
	402   Failed to create security descriptor.
	403   Error creating named pipe.
	404   Error connecting to named pipe.
	405   Error disconnecting named pipe.
	408   Error sending data.
	410   Invalid MaxLineLength value.
	411   Error reading data.
	412   Error invoking RegisterWaitForSingleObject.
	413   Operation would block.
	414   Named pipe does not exist.
	415   Named pipe is already connected.
	416   Error connecting to named pipe.
	417   Named pipe not connected.
	419   Unsupported operation, see error message for details.
	424   Invalid ConnectionID.