Implements an IP Multicast server.

TIdIPMCastServer = class(TIdIPMCastBase)

TIdIPMCastServer is a TIdIPMCastBase descendant that implements an IP multicast server component using the UDP transport, as described in the Internet Standards documents:

• RFC 1112 - Host Extensions for IP Multicasting. (http://www.rfc-editor.org/rfc/rfc1112.txt)

• RFC 1458 - Requirements for Multicast Protocols. (http://www.rfc-editor.org/rfc/rfc1458.txt)

TIdIPMCastServer implements abstract methods from the ancestor class, and provides additional methods and properties used for loopback diagnostics, socket options, and transmission of Multicast datagrams.

Indicates if the multicast server is active and able to transmit datagram packets.

property Active;

Active is a published Boolean property in TIdIPMCastServer that indicates if the multicast server is active and able to transmit datagram packets. Active uses an overriden read access specifier that insures that the Binding for the server has been initialized and the socket handle has been allocated. Active is set to False when the server is freed using Destroy.

Socket descriptor for multicast server transmissions.

property Binding: TIdSocketHandle;

TIdSocketHandle - Socket descriptor for the multicast server.

Binding is a read-only TIdSocketHandle property that represents the socket descriptor used by the multicast server to send datagram packets to multicast clients. The read access specifier for the property insures that the Binding has been initialized, and a datagram socket handle has been allocated and bound using the MulticastGroup address and group membership socket options, as well as the TimeToLive options indicated in the property values. Note: Loopback is set to True during Binding initialization to allow diagnostics.

Indicates if datagrams for the local network module are used for the server.

property Loopback: Boolean;

Loopback is a Boolean property that indicates if Loopback socket options are used on the Binding for the multicast server. Loopback indicates if the local network module can deliver multicast datagram packets that were transmitted from that network module. Changing the value of the Loopback property will result in a change to the socket options for Binding to reflect the new property value. The default value for the Loopback is DEF_IMP_LOOPBACK as assigned in the Create constructor.

Represents the multicast group IP address.

property MulticastGroup;

MulticastGroup is a published property in TIdIPMCastServer that identifies the dotted-decimal representation of the multicast group address for the server. MulticastGroup is used when setting socket options for a binding used by the multicast server, and when transmitting datagram packets to network interface.

MulticastGroup must contain an IP address acceptable to IsValidMulticastGroup, or an exception can be raised when creating, accessing, or releasing the Binding used by the multicast server.

Port number used to send datagram transmissions.

property Port;

Port is a published Integer property in TIdIPMCastServer that represents the port number used when sending datagram transmissions using the Send or SendBuffer method.

Numberof hops allowed across routers and gateways for the datagram transmission.

property TimeToLive: Byte;

TimeToLive is a Byte property that indicates the number of hops permitted in routers and gateways that must handle the datagram transmission. TimeToLive is used to set the socket options for the Binding used by the multicast server. Changing the value of TimeToLive forces an update to the socket options for Binding. The default value of TimeToLive is DEF_IMP_TTL as assigned by the Create constructor.

Constructor for the object instance.

constructor Create(AOwner: TComponent); override;

Owner of the object instance.

Create is the overridden constructor for the object instance. Create calls the inherited Create method using AOwner as the owner of the object instance. Create also assigns the default values for the Loopback (DEF_IMP_LOOPBACK) and TimeToLive (DEF_IMP_TTL) properties.

Frees the object instance.

destructor Destroy; override;

Destroy is the destructor for the object instance. Destroy sets the Active property to False, to insure that the IP address for the local binding is removed as a member of the MultiCast Group address. Destroy calls the inherited Destroy method prior to exiting.

Sends a datagram containing a string value.

procedure Send(AData: string);

String value to be sent in the datagram.

Send is a procedure that allows the multicast server to send a datagram containing the value in AData to the group address specified in the MulticastGroup property. Send calls the MulticastBuffer method using values in the MulticastGroup and Port properties, as well as the value and length indicated in AData.

Use SendBuffer to transmit a datagram containing non-string values.

Sends a datagram containing a non-string value.

procedure SendBuffer(var ABuffer; const AByteCount: integer);

Buffer containing the content for the datagram.

Number of bytes in the buffer to be sent in the datagram.

SendBuffer is a procedure that allows the multicast server to send a datagram containing the non-string value in ABuffer to the group address specified in the MulticastGroup property. Send calls the MulticastBuffer method using values in the MulticastGroup and Port properties, as well as the value and length indicated in ABuffer and AByteCount.

Use Send to transmit a datagram containing a string value.