Specifies a UDP base class.

TIdUDPBase = class(TIdComponent)

TIdUDPBase specifies an encapsulation of the User Datagram Protocol (UDP), and provides properties and methods common to both UDP clients and UDP servers. TIdUDPServer and TIdUDPClient are descendants of TIdUDPBase.

For more information on the User Datagram Protocol (UDP), refer to the Internet Standards document:

• RFC 768 - User Datagram Protocol (UDP) (http://www.rfc-editor.org/rfc/rfc768.txt)

TIdUDPBase implements the common UDP facilities required to create a socket binding using the Socket Datagram protocol family, perform datagram Broadcasts, and handle Host and Port assignments for the connection-less protocol.

Indicates that the socket binding has been allocated.

property Active: Boolean;

Active is a Boolean property used to indicate that the socket binding has been allocated. Note that Active will always return False when using the IDE.

Socket handle for the read or write transaction.

property Binding: TIdSocketHandle;

Binding is a read-only TIdSocketHandle property that represents the socket binding used to send and receive data. Unlike TCP, UDP does not create a permanent connection to the remote computer.

Indicates that the socket binding can perform broadcast transmissions.

property BroadcastEnabled: Boolean;

BroadcastEnabled is a Boolean property used to indicate when the protocol handler is transmitting a datagram destined for all computers on the network. BroadcastEnabled is updated by the Broadcast method, and is used to notify the protocol stack that Binding must include or exclude the socket option for broadcast transmissions.

Specifies the largest UDP packet size.

property BufferSize: Integer;

BufferSize is an Integer property used to specify the largest UDP packet that can be sent or received using Binding. The default value for BufferSize is 8192, and is assigned in Create.

An EIdSocketError exception will be raised if ReceiveString encounters a packet larger than BufferSize.

Timeout value for reading from a peer.

property ReceiveTimeout: Integer;

ReceiveTimeout is an Integer property used to reflect the number of milliseconds to wait for the socket Binding to become readable in the ReceiveString method. The default value for ReceiveTimeout is TIdTimeoutInfinite as assigned in Create.

Send data to all computers on the network.

procedure Broadcast(const AData: string; const APort: integer);

Values to send in the datagram.

Port number for the transmission.

Broadcast is a procedure used to send the data specified in AData using the port number specified in APort. Broadcast sends the data to all computers on the network. Note: Many network routers will not forward UDP broadcasts beyond the boundaries of the local network.

Broadcast calls the Send method using the reserved network address '255.255.255.255' as the destination. Broadcast also maintains BroadcastEnabled to indicate the current transaction state.

Constructor for the object instance.

constructor Create(AOwner: TComponent); override;

Owner of the object instance.

Create is the constructor for the object instance, and relies on the inherited Create method to initialize object properties. Create sets the default value for BufferSize to 8192, and ReceiveTimeout to IdTimeoutInfinite.

Frees an object instance.

destructor Destroy; override;

Destroy is the destructor for the object instance. Destroy insures that the Active property is set to False, and calls the inherited Destroy method to finalize object destruction.

Reads data from a remote connection.

function ReceiveBuffer(var ABuffer; const ABufferSize: Integer; const AMSec: Integer = IdTimeoutDefault): integer; overload;
function ReceiveBuffer(var ABuffer; const ABufferSize: Integer; var VPeerIP: string; var VPeerPort: integer; AMSec: Integer = IdTimeoutDefault): integer; overload;

Buffer where received data is stored.

Number of bytes to read from the remote connection.

Milliseconds to wait for a readable connection. The default value is IdTimeoutDefault.

IP address for the remote connection.

Port number for the remote connection.

Integer - Bytes read from the remote connection.

ReceiveBuffer is an Integer function used to read data from the remote connection specified in VPeerIP and VPeerPort into the buffer ABuffer.

ABufferSize indicates the number of bytes to read from the remote connection.

AMSec indicates the number of milliseconds to delay while waiting for the socket Binding to become Readable. The default value for AMSec is IdTimeoutDefault, and indicates that ReceiveTimeOut will be used as the timeout value.

If a timeout occurs while waiting for the Binding to become ready for the read operation, RecvBuffer will set the following values before exiting the method:

• Result - zero (0),

• VPeerIP - empty string ('')

• VPeerPort - zero (0)

If RecvBuffer is unable to read data from the remote connection, an EIdUDPReceiveErrorZeroBytes exception will be raised.

Reads data from a remote connection.

function ReceiveBuffer(var ABuffer; const ABufferSize: Integer; const AMSec: Integer = IdTimeoutDefault): integer; overload;
function ReceiveBuffer(var ABuffer; const ABufferSize: Integer; var VPeerIP: string; var VPeerPort: integer; AMSec: Integer = IdTimeoutDefault): integer; overload;

Buffer where received data is stored.

Number of bytes to read from the remote connection.

Milliseconds to wait for a readable connection. The default value is IdTimeoutDefault.

IP address for the remote connection.

Port number for the remote connection.

Integer - Bytes read from the remote connection.

ReceiveBuffer is an Integer function used to read data from the remote connection specified in VPeerIP and VPeerPort into the buffer ABuffer.

ABufferSize indicates the number of bytes to read from the remote connection.

AMSec indicates the number of milliseconds to delay while waiting for the socket Binding to become Readable. The default value for AMSec is IdTimeoutDefault, and indicates that ReceiveTimeOut will be used as the timeout value.

If a timeout occurs while waiting for the Binding to become ready for the read operation, RecvBuffer will set the following values before exiting the method:

• Result - zero (0),

• VPeerIP - empty string ('')

• VPeerPort - zero (0)

If RecvBuffer is unable to read data from the remote connection, an EIdUDPReceiveErrorZeroBytes exception will be raised.

Reads data from the remote computer.

function ReceiveString(const AMSec: Integer = IdTimeoutDefault): string; overload;
function ReceiveString(var VPeerIP: string; var VPeerPort: integer; const AMSec: Integer = IdTimeoutDefault): string; overload;

Timeout value for the read operation. Default value is IdTimeoutDefault.

Address of the remote computer.

Port number of the remote computer.

String - Data received from the remote computer.

ReceiveString is a String function used to receive data from a remote computer system.

VPeerIP is updated to reflect the IP address on the remote computer where the data originated. VPeerPort is updated to reflect the port number on the remote computer where the data originated.

If AMSec is omitted, the default timeout value used is ReceiveTimeout. Use TIdTimeoutInfinite to disable read timeout. If a timeout occurs while waiting for the socket Binding to become readable, VPeerIP is set to '' and VPeerPort is set to 0 before exiting from the method.

ReceiveString will read up to BufferSize bytes from the remote computer.

ReceiveString will raise an EIdException exception if the number of bytes read from the remote computer is 0.

Reads data from the remote computer.

function ReceiveString(const AMSec: Integer = IdTimeoutDefault): string; overload;
function ReceiveString(var VPeerIP: string; var VPeerPort: integer; const AMSec: Integer = IdTimeoutDefault): string; overload;

Timeout value for the read operation. Default value is IdTimeoutDefault.

Address of the remote computer.

Port number of the remote computer.

String - Data received from the remote computer.

ReceiveString is a String function used to receive data from a remote computer system.

VPeerIP is updated to reflect the IP address on the remote computer where the data originated. VPeerPort is updated to reflect the port number on the remote computer where the data originated.

If AMSec is omitted, the default timeout value used is ReceiveTimeout. Use TIdTimeoutInfinite to disable read timeout. If a timeout occurs while waiting for the socket Binding to become readable, VPeerIP is set to '' and VPeerPort is set to 0 before exiting from the method.

ReceiveString will read up to BufferSize bytes from the remote computer.

ReceiveString will raise an EIdException exception if the number of bytes read from the remote computer is 0.

Sends data to a remote computer system.

procedure Send(AHost: string; const APort: Integer; const AData: string);

Address of the remote computer.

Port number on the remote computer.

Value to send to the remote computer.

Send is a procedure used to send the data specified in AData to the remote computer system specified in AHost and APort. Send will resolve the address in AHost to a host name prior to sending AData to the remote system.

Send calls Binding.SendTo to transmit AData to the remote system. UDP does not guarantee delivery of data packets, so the values in AData may not arrive at the remote computer system.

Sends data to a remote host.

procedure SendBuffer(AHost: string; const APort: Integer; var ABuffer; const AByteCount: integer);

Address for the remote connection.

Port number for the remote connection.

Data to be sent to the remote connection.

Number of bytes to send to the remote connection.

SendBuffer is a procedure used to transmit data to a remote connection. AHost and APort identify the remote system that is the endpoint for the connection. Before transmitting data, SendBuffer will use the protocol stack to resolve the host name in AHost to an IP address.

ABuffer contains the data to be transmitted to the remote host.

SendBuffer uses the TIdSocketHandle.SendTo method for the socket binding to transmit data.