org.jcsp.lang
Interface ConnectionClient

All Known Subinterfaces:

NetConnectionClient, NetSharedConnectionClient, SharedConnectionClient

All Known Implementing Classes:

AltingConnectionClient, AltingConnectionClientImpl, NetAltingConnectionClient, NetSharedAltingConnectionClient, SharedAltingConnectionClient

public interface ConnectionClient

This is an interface to be implemented by classes that wish to act as a client to connect to a ConnectionServer.

Users of classes implementing this interface should call request(Object) to initiate a conversation and to send some data to the server. Implementations may decide to return immediately or to wait until the server accepts the connection and then return. The Connection is not guaranteed to be open until a call to reply() has returned. The reply() method should be called soon after the call to reqeust(Object). Some computation may be done between the calls but any external process synchronization is potentially hazardous.

After calling reply(), clients can check whether the server closed the connection by calling isOpen(). If it returns true, then the connection has been kept open. If the connection has been kept open then the client may assume that a call to request(Object) will not block and that the connection will soon be dealt with by the server.

This is an example of typical code structure for using a ConnectionClient:

 //have a variable client of type ConnectionClient
 do {
     client.request(some_data);
     some_variable = client.receive();
 } while (client.isOpen())
 

Author:

Quickstone Technologies Limited

Method Summary

boolean	isOpen() Returns whether the server has kept its end of the Connection open.
Object	reply() Receives some data back from the server after request(Object) has been called.
void	request(Object data) This method is used to send data to a ConnectionServer in a client/server conversation.

Method Detail

request

void request(Object data)
             throws IllegalStateException

This method is used to send data to a ConnectionServer in a client/server conversation. If a connection has not yet been established, then this method will open the connection as necessary.

Once this method has returned, the client may do some computation but must then guarantee to call reply(). This will obtain a server's response to the request. In between calling this method and reply(), doing pure computation is safe. Performing synchronization with other process is potentially hazardous.

Once a server replies, if the connection has been kept open, then this method should be called again to make a further request.

Programs using Connections need to adopt a protocol so that the server knows when a conversation with a client has finished and will then drop the connection.

Parameters:

data - the Object to send to the server.

Throws:

IllegalStateException - if the method is called when it is not meant to be.

reply

Object reply()
             throws IllegalStateException

Receives some data back from the server after request(Object) has been called.

After calling this method, isOpen() may be called to establish whether the server dropped the connection after replying.

Implementations may make this operation ALTable.

Returns:

the Object sent from the server.

Throws:

IllegalStateException - if the method is called when it is not meant to be.

isOpen

boolean isOpen()
               throws IllegalStateException

Returns whether the server has kept its end of the Connection open. This should only be called after a call to reply() and before any other Connection method is called.

Returns:

true iff the server has kept the connection open.

Throws:

IllegalStateException