The Telnet Protocol control enables an application to connect to a Telnet server, which provides an interactive terminal session similar to how character based consoles and terminals work. The user can login, enter commands and interact with applications programmatically or in conjunction with the terminal emulation control.
Initialize
Initialize an instance of the class, loading the networking library
and validating the development license. This method must be called
before any properties are changed or any other methods in this
class are called by the application.
Connect
Establish a connection to the server. Once the connection has been
established, the other methods in the class may be used to exchange
data with the server.
Disconnect
Disconnect from the server and release the memory allocated for
that client session. After this method is called, the client
session is no longer valid.
Reset
Reset the internal state of the component. This can be useful if
your application wishes to discard any settings made by a user and
return that instance of the class to its default state.
Uninitialize
Unload the networking library and release any resources that have
been allocated for the current process. This is the last method
call that the application should make prior to terminating. This is
only necessary if the application has previously called the
Initialize method.
Once connected to the Telnet server, any output generated by a program on the server will be sent as data for the client to read. Any input to the program is sent by the client and received and processed by the server. The following methods are used:
Read
Reads any output that has been generated by the program executing
on the server. When the client first connects, the server typically
executes a login program that requests the users authenticate
themselves by entering a user name and password. Once the user has
logged in, they are usually given a command line prompt where they
can enter commands to be executed on the server. If the server
closes the connection, the Read method will indicate that with an
error result and the client can disconnect from the server at that
point.
Write
Send data to the Telnet server which will be received as input to
the program. If the local echo option is enabled, then the client
is also responsible for writing the input data to the display
device, if there is one. If local echo is not enabled, the server
will automatically echo back any characters written as data to be
read by the client.
Telnet supports a mode of operation where the it is the responsibility of the client to echo any data sent to the server. This is controlled by the LocalEcho property.
LocalEcho
If this property is set to True, it is the responsibility of the
client to echo any data that it is sending to the server. For
example, if the character "A" is sent to the server, the
application must also send the character "A" to whatever interface
the user is interacting with, such as a terminal emulation window.
The default mode is for this option to be disabled, which means
that the server will echo back any data that is sent to it.
The Telnet protocol can be used to connect to a server, log in and execute one or more commands, process the output from those commands and display it to an end-user using a graphical interface. The user never sees or interacts with the actual terminal session. The Telnet interface provides methods which can simplify this kind of application, reducing the amount of code needed to process the data stream returned by the server.
Login
This method is used to automatically log a user in, using the
specific user name and password. This method is specifically
designed for UNIX based servers or Windows servers which emulate
the same basic login sequence.
Search
This method is used to search for a specific character or sequence
of characters in the data stream returned by the server. The
control will accumulate all of the data received up to the point
where the character sequence is encountered. This can be used to
capture all of the output from a command, or search for specific
results returned by the command as it executes on the server.