MCast Component

The MCast control is used to multicast UDP datagrams to multicast capable hosts in multicast capable subnets. It can act both as a client and a server and communicate with any number of hosts simultaneously, as well as generate and receive broadcast packets. (NOTE: The following is a very short description. For more information, please consult the help files that come with the respective package.)

The MCast control is very similar to UDPPort, except for some additional properties that provide support for multicast datagrams. To send datagrams to a multicast group, simply assign the address of the group to RemoteHost. To receive datagrams from one or more groups, assign the group addresses to MulticastGroup one by one (after the control is activated. TimeToLive allows to specify how many subnets a packet should be allowed to receive. ReceiveInterface and SendInterface allow you to select the network interface for multicast operations.

The control is activated/deactivated through the Active property. This property enables or disables sends or receives. The data can be sent in the same way as UDPPort, by using the DataToSend property. The destination is specified using the RemoteHost and RemotePort properties. Inbound data is received through the DataIn event.

This control requires a Winsock 1.1 compliant TCP/IP stack. This means that the Winsock stack installed in the system must have a version of at least 1.1. In particular, Windows 95, 98, and NT machines with Winsock 2.0 are fully supported.

PROPERTIES

AcceptData. Enables or disables data reception (the DataIn event).

Active. Enables or disables sending and receiving of data. Action property.

DataToSend. A string of data to be sent to the remote host. Write-only property.

InBufferSize. The size in bytes of the incoming queue of the socket.

LocalHost. The name of the local host or user-assigned IP interface through which connections are accepted or initiated.

LocalPort. The UDP port in the local host where MCast binds.

Loopback. Enables or disables loopback of data sent to the multicast group.

MaxPacketSize. The maximum length of the packets that can be received.

MulticastGroup. Multicast group to join or leave.

OutBufferSize. The size in bytes of the outgoing queue of the socket.

ReceiveInterface. The interface where to receive multicast packets into. If empty, default is used.

RemoteHost. The address of the remote host (multicast group).

RemotePort. The UDP port in the remote host.

SendInterface. The interface where to send multicast packets from. If empty, default is used.

SocketHandle. The handle of the main socket used by the control.

TimeToLive. The maximum number of subnets that a multicast datagram can traverse.

WinsockInfo. Identifying information about the loaded Winsock stack.

WinsockLoaded. Loads and unloads Winsock on demand.

WinsockMaxDatagramSize. Size in bytes of the largest UDP datagram that can be sent or received.

WinsockMaxSockets. Maximum number of sockets available to a single process.

WinsockPath. The path to the Winsock DLL used.

WinsockStatus. The status of the Winsock stack.

EVENTS

DataIn. Fired when data is received.

Error. Information about errors during data delivery.

ReadyToSend. Fired when the control is ready to send data.