Telnet Component

Properties   Methods   Events   Config Settings   Errors  

The Telnet Component is used to communicate with servers implementing the TELNET protocol.

Syntax

TipsTelnet

Remarks

The Telnet Component supports both plaintext and SSL/TLS connections. When connecting over SSL/TLS the SSLServerAuthentication event allows you to check the server identity and other security attributes. The SSLStatus event provides information about the SSL handshake. Additional SSL related settings are also supported via the Config method.

The Telnet Component provides a simple interface to Telnet communications as specified by RFC 854. It allows sending of Telnet command codes to remote Telnet servers and it scans the input data for Telnet commands. Appropriate events are fired for received commands.

The connection interface is very similar to that of TCPClient. The same properties and events are used for sending and receiving normal data, and the same property set is used for setting properties of the connection. The Telnet Component adds a number of properties like Command, DoOption, etc. which allow sending of Telnet commands to the other end. The respective events (Command, Do, etc.) are fired when the corresponding Telnet commands are received.

Property List

The following is the full list of the properties of the component with short descriptions. Click on the links for further details.

Method List

The following is the full list of the methods of the component with short descriptions. Click on the links for further details.

Event List

The following is the full list of the events fired by the component with short descriptions. Click on the links for further details.

Config Settings

The following is a list of config settings for the component with short descriptions. Click on the links for further details.

AcceptData Property (Telnet Component)

This property enables or disables data reception (the DataIn event).

Syntax

property AcceptData: Boolean read get_AcceptData write set_AcceptData;

Default Value

true

Remarks

This property enables or disables data reception (the DataIn event). Setting this property to False, temporarily disables data reception (and the DataIn event). Setting this property to True, reenables data reception.

Note: It is recommended to use the PauseData or ProcessData method instead of setting this property.

This property is not available at design time.

BytesSent Property (Telnet Component)

The number of bytes actually sent after an assignment to DataToSend .

Syntax

property BytesSent: Integer read get_BytesSent;

Default Value

0

Remarks

The BytesSent property shows how many bytes were sent after the last assignment to DataToSend or UrgentData. Please check the DataToSend property for more information.

This property is read-only and not available at design time.

Command Property (Telnet Component)

A single character Telnet command code to be sent to the server.

Syntax

property Command: Integer write set_Command;

Default Value

0

Remarks

Codes for Telnet commands and their meanings are defined in the Telnet RFCs. Here are some examples:

This property is write-only and not available at design time.

Connected Property (Telnet Component)

Triggers a connection or disconnection.

Syntax

property Connected: Boolean read get_Connected write set_Connected;

Default Value

false

Remarks

Setting the Connected property to True makes the component attempt to connect to the host identified by the RemoteHost property. If successful, after the connection is achieved, the value of the property changes to True and the Connected event is fired.

Setting Connected to False closes the connection. How and when the connection is closed is controlled by the Linger property.

Note: It is recommended to use the Connect or Disconnect method instead of setting this property.

This property is not available at design time.

DataToSend Property (Telnet Component)

A string of data to be sent to the remote host.

Syntax

property DataToSend: String write set_DataToSend;
property DataToSendB: TBytes write set_DataToSendB;

Default Value

''

Remarks

Assigning a string to the DataToSend property makes the component send the string to the remote host. The Send method provides similar functionality.

If you are sending data to the remote host faster than it can process it, or faster than the network's bandwidth allows, the outgoing queue might fill up. When this happens, the operation raises the exception with errorcode 10035 and message '[10035] Operation would block' (WSAEWOULDBLOCK). You can handle this exception, and then try to send the data again. . The BytesSent property shows how many bytes were sent (if any). If 0 bytes were sent, then you can wait for the ReadyToSend event before attempting to send data again.

Note: The ReadyToSend event is not fired when part of the data is sent successfully.

This property is write-only and not available at design time.

DontOption Property (Telnet Component)

A single character Telnet option code to be sent to the server with the Telnet DONT command.

Syntax

property DontOption: Integer write set_DontOption;

Default Value

0

Remarks

For a list of option codes and their descriptions, please look at the Telnet RFCs. The following are a few examples:

This property is write-only and not available at design time.

DoOption Property (Telnet Component)

A single character Telnet option code to be sent to the server with the Telnet DO command.

Syntax

property DoOption: Integer write set_DoOption;

Default Value

0

Remarks

For a list of option codes and their descriptions, please look at the Telnet RFCs. The following are a few examples:

This property is write-only and not available at design time.

DoSubOption Property (Telnet Component)

A Telnet SubOption to send to the server with the SubOption command.

Syntax

property DoSubOption: String write set_DoSubOption;
property DoSubOptionB: TBytes write set_DoSubOptionB;

Default Value

''

Remarks

For a list of valid Telnet suboptions and their descriptions please look at the Telnet RFCs.

You don't need to specify the suboption start and suboption end codes. Those are appended automatically by the component. For example, to send a terminal type suboption to request setting the terminal type to 'vt100', you must send ASCII 24, followed by ASCII 0, followed by "vt100" (without the quotes).

This property is write-only and not available at design time.

Firewall Property (Telnet Component)

A set of properties related to firewall access.

Syntax

property Firewall: TipsFirewall read get_Firewall write set_Firewall;

Remarks

This is a Firewall-type property, which contains fields describing the firewall through which the component will attempt to connect.

KeepAlive Property (Telnet Component)

When True, KEEPALIVE packets are enabled (for long connections).

Syntax

property KeepAlive: Boolean read get_KeepAlive write set_KeepAlive;

Default Value

false

Remarks

The KeepAlive enables the SO_KEEPALIVE option on the socket. This option prevents long connections from timing out in case of inactivity.

Note: System Transmission Control Protocol (TCP)/IP stack implementations are not required to support SO_KEEPALIVE.

Linger Property (Telnet Component)

When set to True, this property ensures that connections are terminated gracefully.

Syntax

property Linger: Boolean read get_Linger write set_Linger;

Default Value

true

Remarks

This property controls how a connection is closed. The default is True.

In the case that Linger is True (default), two scenarios determine how long the connection will linger. In the first, if LingerTime is 0 (default), the system will attempt to send pending data for a connection until the default IP timeout expires.

In the second scenario, if LingerTime is a positive value, the system will attempt to send pending data until the specified LingerTime is reached. If this attempt fails, then the system will reset the connection.

The default behavior (which is also the default mode for stream sockets) might result in a long delay in closing the connection. Although the component returns control immediately, the system could hold system resources until all pending data are sent (even after your application closes).

Setting this property to False forces an immediate disconnection. If you know that the other side has received all the data you sent (e.g., by a client acknowledgment), setting this property to False might be the appropriate course of action.

LocalHost Property (Telnet Component)

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

Syntax

property LocalHost: String read get_LocalHost write set_LocalHost;

Default Value

''

Remarks

The LocalHost property contains the name of the local host as obtained by the gethostname() system call, or if the user has assigned an IP address, the value of that address.

In multi-homed hosts (machines with more than one IP interface) setting LocalHost to the value of an interface will make the component initiate connections (or accept in the case of server components) only through that interface.

If the component is connected, the LocalHost property shows the IP address of the interface through which the connection is made in internet dotted format (aaa.bbb.ccc.ddd). In most cases, this is the address of the local host, except for multi-homed hosts (machines with more than one IP interface).

NOTE: LocalHost is not persistent. You must always set it in code, and never in the property window.

LocalPort Property (Telnet Component)

The TCP port in the local host where TCPClient binds.

Syntax

property LocalPort: Integer read get_LocalPort write set_LocalPort;

Default Value

0

Remarks

The LocalPort property must be set before a connection is attempted. It instructs the component to bind to a specific port (or communication endpoint) in the local machine.

Setting it to 0 (default) enables the TCP/IP stack to choose a port at random. The chosen port will be shown by the LocalPort property after the connection is established.

LocalPort cannot be changed once a connection is made. Any attempt to set the LocalPort property when a connection is active will generate an error.

The LocalPort property is useful when trying to connect to services that require a trusted port in the client side.

RemoteHost Property (Telnet Component)

This property includes the address of the remote host. Domain names are resolved to IP addresses.

Syntax

property RemoteHost: String read get_RemoteHost write set_RemoteHost;

Default Value

''

Remarks

This property specifies the IP address (IP number in dotted internet format) or the domain name of the remote host. It is set before a connection is attempted and cannot be changed once a connection is established.

If this property is set to a domain name, a DNS request is initiated, and upon successful termination of the request, this property is set to the corresponding address. If the search is not successful, an error is returned.

If the component is configured to use a SOCKS firewall, the value assigned to this property may be preceded with an "*". If this is the case, the host name is passed to the firewall unresolved and the firewall performs the DNS resolution.

Example. Connecting:

TCPClientControl.RemoteHost = "MyHostNameOrIP" TCPClientControl.RemotePort = 777 TCPClientControl.Connected = true

RemotePort Property (Telnet Component)

The secure Telnet port in the remote host (default is 23).

Syntax

property RemotePort: Integer read get_RemotePort write set_RemotePort;

Default Value

23

Remarks

For implicit SSL, use port 992 (please refer to the SSLStartMode property for more information).

A valid port number (a value between 1 and 65535) is required for the connection to take place. The property must be set before a connection is attempted and cannot be changed once a connection is established. Any attempt to change this property while connected will fail with an error.

This property is not available at design time.

SSLAcceptServerCertEncoded Property (Telnet Component)

This is the certificate (PEM/base64 encoded).

Syntax

property SSLAcceptServerCertEncoded: String read get_SSLAcceptServerCertEncoded write set_SSLAcceptServerCertEncoded;
property SSLAcceptServerCertEncodedB: TBytes read get_SSLAcceptServerCertEncodedB write set_SSLAcceptServerCertEncodedB;

Default Value

''

Remarks

This is the certificate (PEM/Base64 encoded). This property is used to assign a specific certificate. The Store and Subject properties also may be used to specify a certificate.

When Encoded is set, a search is initiated in the current Store for the private key of the certificate. If the key is found, Subject is updated to reflect the full subject of the selected certificate; otherwise, Subject is set to an empty string.

This property is not available at design time.

SSLCertEncoded Property (Telnet Component)

This is the certificate (PEM/base64 encoded).

Syntax

property SSLCertEncoded: String read get_SSLCertEncoded write set_SSLCertEncoded;
property SSLCertEncodedB: TBytes read get_SSLCertEncodedB write set_SSLCertEncodedB;

Default Value

''

Remarks

This is the certificate (PEM/Base64 encoded). This property is used to assign a specific certificate. The Store and Subject properties also may be used to specify a certificate.

When Encoded is set, a search is initiated in the current Store for the private key of the certificate. If the key is found, Subject is updated to reflect the full subject of the selected certificate; otherwise, Subject is set to an empty string.

This property is not available at design time.

SSLCertStore Property (Telnet Component)

This is the name of the certificate store for the client certificate.

Syntax

property SSLCertStore: String read get_SSLCertStore write set_SSLCertStore;
property SSLCertStoreB: TBytes read get_SSLCertStoreB write set_SSLCertStoreB;

Default Value

'MY'

Remarks

This is the name of the certificate store for the client certificate.

The StoreType property denotes the type of the certificate store specified by Store. If the store is password protected, specify the password in StorePassword.

Store is used in conjunction with the Subject property to specify client certificates. If Store has a value, and Subject or Encoded is set, a search for a certificate is initiated. Please see the Subject property for details.

Designations of certificate stores are platform dependent.

The following designations are the most common User and Machine certificate stores in Windows:

When the certificate store type is PFXFile, this property must be set to the name of the file. When the type is PFXBlob, the property must be set to the binary contents of a PFX file (i.e., PKCS#12 certificate store).

SSLCertStorePassword Property (Telnet Component)

If the type of certificate store requires a password, this property is used to specify the password needed to open the certificate store.

Syntax

property SSLCertStorePassword: String read get_SSLCertStorePassword write set_SSLCertStorePassword;

Default Value

''

Remarks

If the type of certificate store requires a password, this property is used to specify the password needed to open the certificate store.

SSLCertStoreType Property (Telnet Component)

This is the type of certificate store for this certificate.

Syntax

property SSLCertStoreType: TipsCertStoreTypes read get_SSLCertStoreType write set_SSLCertStoreType;

TipsCertStoreTypes = (
  cstUser,
  cstMachine,
  cstPFXFile,
  cstPFXBlob,
  cstJKSFile,
  cstJKSBlob,
  cstPEMKeyFile,
  cstPEMKeyBlob,
  cstPublicKeyFile,
  cstPublicKeyBlob,
  cstSSHPublicKeyBlob,
  cstP7BFile,
  cstP7BBlob,
  cstSSHPublicKeyFile,
  cstPPKFile,
  cstPPKBlob,
  cstXMLFile,
  cstXMLBlob,
  cstJWKFile,
  cstJWKBlob,
  cstSecurityKey,
  cstBCFKSFile,
  cstBCFKSBlob,
  cstPKCS11,
  cstAuto
);

Default Value

cstUser

Remarks

This is the type of certificate store for this certificate.

The component supports both public and private keys in a variety of formats. When the cstAuto value is used, the component will automatically determine the type. This property can take one of the following values:

SSLCertSubject Property (Telnet Component)

This is the subject of the certificate used for client authentication.

Syntax

property SSLCertSubject: String read get_SSLCertSubject write set_SSLCertSubject;

Default Value

''

Remarks

This is the subject of the certificate used for client authentication.

This property must be set after all other certificate properties are set. When this property is set, a search is performed in the current certificate store to locate a certificate with a matching subject.

If a matching certificate is found, the property is set to the full subject of the matching certificate.

If an exact match is not found, the store is searched for subjects containing the value of the property.

If a match is still not found, the property is set to an empty string, and no certificate is selected.

The special value "*" picks a random certificate in the certificate store.

The certificate subject is a comma-separated list of distinguished name fields and values. For instance, "CN=www.server.com, OU=test, C=US, E=support@nsoftware.com". Common fields and their meanings are as follows:

If a field value contains a comma, it must be quoted.

SSLProvider Property (Telnet Component)

This specifies the SSL/TLS implementation to use.

Syntax

property SSLProvider: TipsTSSLProviders read get_SSLProvider write set_SSLProvider;

TipsTSSLProviders = (
  sslpAutomatic,
  sslpPlatform,
  sslpInternal
);

Default Value

sslpAutomatic

Remarks

This property specifies the SSL/TLS implementation to use. In most cases the default value of 0 (Automatic) is recommended and should not be changed. When set to 0 (Automatic) the component will select whether to use the platform implementation or the internal implementation depending on the operating system as well as the TLS version being used.

Possible values are:

In most cases using the default value (Automatic) is recommended. The component will select a provider depending on the current platform.

When Automatic is selected, on Windows the component will use the platform implementation. On Linux/macOS the component will use the internal implementation. When TLS 1.3 is enabled via SSLEnabledProtocols the internal implementation is used on all platforms.

SSLServerCertEncoded Property (Telnet Component)

This is the certificate (PEM/base64 encoded).

Syntax

property SSLServerCertEncoded: String read get_SSLServerCertEncoded;
property SSLServerCertEncodedB: TBytes read get_SSLServerCertEncodedB;

Default Value

''

Remarks

This is the certificate (PEM/Base64 encoded). This property is used to assign a specific certificate. The Store and Subject properties also may be used to specify a certificate.

When Encoded is set, a search is initiated in the current Store for the private key of the certificate. If the key is found, Subject is updated to reflect the full subject of the selected certificate; otherwise, Subject is set to an empty string.

This property is read-only and not available at design time.

SSLStartMode Property (Telnet Component)

Determines how the component starts the SSL negotiation.

Syntax

property SSLStartMode: TipsTSSLStartModes read get_SSLStartMode write set_SSLStartMode;

TipsTSSLStartModes = (
  sslAutomatic,
  sslImplicit,
  sslExplicit
);

Default Value

sslAutomatic

Remarks

The SSLStartMode property may have one of the following values:

Timeout Property (Telnet Component)

A timeout for the component.

Syntax

property Timeout: Integer read get_Timeout write set_Timeout;

Default Value

0

Remarks

If the Timeout property is set to 0, all operations return immediately, potentially failing with an 'WOULDBLOCK' error if data can't be sent or received immediately.

If Timeout is set to a positive value, the component will automatically retry each operation that would otherwise result in a 'WOULDBLOCK' error for a maximum of Timeout seconds.

The component will use DoEvents to enter an efficient wait loop during any potential waiting period, making sure that all system events are processed immediately as they arrive. This ensures that the host application does not "freeze" and remains responsive.

If Timeout expires, and the operation is not yet complete, the component raises an exception.

Please note that by default, all timeouts are inactivity timeouts, i.e. the timeout period is extended by Timeout seconds when any amount of data is successfully sent or received.

The default value for the Timeout property is 0 (asynchronous operation).

Transparent Property (Telnet Component)

When True, Telnet command processing is disabled.

Syntax

property Transparent: Boolean read get_Transparent write set_Transparent;

Default Value

false

Remarks

The Transparent property allows you to enable or disable Telnet command processing. When command processing is disabled, any data received is provided with no modifications.

UrgentData Property (Telnet Component)

A string of data to be sent urgently (out-of-band) to the remote host.

Syntax

property UrgentData: String write set_UrgentData;
property UrgentDataB: TBytes write set_UrgentDataB;

Default Value

''

Remarks

The UrgentData property behaves exactly like the DataToSend property except that the data is sent Out Of Band (urgent). This means that the data assigned to UrgentData will bypass the normal TCP queuing mechanism. Use this property with caution.

This property is write-only and not available at design time.

WillOption Property (Telnet Component)

A single character Telnet option code to be sent to the server with the Telnet WILL command.

Syntax

property WillOption: Integer write set_WillOption;

Default Value

0

Remarks

For a list of option codes and their descriptions, please look at the Telnet RFCs. The following are a few examples:

This property is write-only and not available at design time.

WontOption Property (Telnet Component)

A single character Telnet option code to be sent to the server with the Telnet WONT command.

Syntax

property WontOption: Integer write set_WontOption;

Default Value

0

Remarks

For a list of option codes and their descriptions, please look at the Telnet RFCs. The following are a few examples:

This property is write-only and not available at design time.

Config Method (Telnet Component)

Sets or retrieves a configuration setting.

Syntax

function Config(ConfigurationString: String): String;

Remarks

Config is a generic method available in every component. It is used to set and retrieve configuration settings for the component.

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the component, access to these internal properties is provided through the Config method.

To set a configuration setting named PROPERTY, you must call Config("PROPERTY=VALUE"), where VALUE is the value of the setting expressed as a string. For boolean values, use the strings "True", "False", "0", "1", "Yes", or "No" (case does not matter).

To read (query) the value of a configuration setting, you must call Config("PROPERTY"). The value will be returned as a string.

Connect Method (Telnet Component)

Connects to a remote host.

Syntax

procedure Connect();

Remarks

This method connects to the remote host specified by RemoteHost. For instance: component.RemoteHost = "MyHostNameOrIP"; component.Connect();

To specify a non-standard port number set RemotePort before calling this method.

ConnectTo Method (Telnet Component)

Connects to a remote host.

Syntax

procedure ConnectTo(Host: String);

Remarks

This method connects to the remote host specified by the Host. For instance: component.Connect("MyTelnetServer");

To specify a non-standard port number set RemotePort before calling this method.

Disconnect Method (Telnet Component)

Disconnect from the remote host.

Syntax

procedure Disconnect();

Remarks

Calling this method is equivalent to setting the Connected property to False.

DoEvents Method (Telnet Component)

Processes events from the internal message queue.

Syntax

procedure DoEvents();

Remarks

When DoEvents is called, the component processes any available events. If no events are available, it waits for a preset period of time, and then returns.

PauseData Method (Telnet Component)

This method pauses data reception.

Syntax

procedure PauseData();

Remarks

This method pauses data reception when called. While data reception is paused, the DataIn event will not fire. Call ProcessData to reenable data reception.

ProcessData Method (Telnet Component)

This method reenables data reception after a call to PauseData .

Syntax

procedure ProcessData();

Remarks

This method reenables data reception after a previous call to PauseData. When PauseData is called, the DataIn event will not fire. To reenable data reception and allow DataIn to fire, call this method.

Note: This method is used only after previously calling PauseData. It does not need to be called to process incoming data by default.

Reset Method (Telnet Component)

Reset the component.

Syntax

procedure Reset();

Remarks

This method will reset the component's properties to their default values.

Send Method (Telnet Component)

Sends binary data to the remote host.

Syntax

procedure Send(Text: TBytes);

Remarks

This method sends the specified binary data to the remote host. To send text use the SendText method instead.

SendBytes Method (Telnet Component)

Sends binary data to the remote host.

Syntax

procedure SendBytes(Data: TBytes);

Remarks

This method sends the specified binary data to the remote host. To send text use the SendText method instead.

SendCommand Method (Telnet Component)

Sends a single character Telnet command code to the server.

Syntax

procedure SendCommand(Command: Integer);

Remarks

This method sends the single character command code specified by Command to the server. Codes for Telnet commands and their meanings are defined in the Telnet RFCs. Some common commands are:

SendDontOption Method (Telnet Component)

This method sends a single character Telnet option code to the server with the Telnet DONT command.

Syntax

procedure SendDontOption(DontOption: Integer);

Remarks

For a list of option codes and their descriptions, please look at the Telnet RFCs. The following are a few examples:

SendDoOption Method (Telnet Component)

This method sends a single character Telnet option code to the server with the Telnet DO command.

Syntax

procedure SendDoOption(DoOption: Integer);

Remarks

For a list of option codes and their descriptions, please look at the Telnet RFCs. The following are a few examples:

SendDoSubOption Method (Telnet Component)

This methods sends a Telnet SubOption to send to the server with the SubOption command.

Syntax

procedure SendDoSubOption(DoSubOption: TBytes);

Remarks

Valid suboptions and their descriptions are defined in the Telnet RFCs.

For example, to send a terminal type suboption to request setting the terminal type to 'vt100', send ASCII 24, followed by ASCII 0, followed by vt100.

Suboption start and end codes are automatically added by the component.

SendText Method (Telnet Component)

Sends text to the remote host.

Syntax

procedure SendText(Text: String);

Remarks

This method sends the specified text to the remote host. To send binary data use the SendBytes method instead.

SendUrgentBytes Method (Telnet Component)

Urgently sends binary data to the remote host.

Syntax

procedure SendUrgentBytes(UrgentBytes: TBytes);

Remarks

This method sends the bytes specified by UrgentBytes as urgent data (out-of-band) to the remote host. To send text urgently use the SendUrgentText method instead.

Data sent using this method will bypass the normal TCP queuing mechanism. Use this method with caution.

SendUrgentText Method (Telnet Component)

Urgently sends text to the remote host.

Syntax

procedure SendUrgentText(UrgentText: String);

Remarks

This method sends the text specified by UrgentText as urgent data (out-of-band) to the remote host. To send binary data urgently use the SendUrgentBytes method instead.

Data sent using this method will bypass the normal TCP queuing mechanism. Use this method with caution.

SendWillOption Method (Telnet Component)

This method sends a single character Telnet option code the server with the Telnet WILL command.

Syntax

procedure SendWillOption(WillOption: Integer);

Remarks

For a list of option codes and their descriptions, please look at the Telnet RFCs. The following are a few examples:

SendWontOption Method (Telnet Component)

This method sends a single character Telnet option code to the server with the Telnet WONT command.

Syntax

procedure SendWontOption(WontOption: Integer);

Remarks

For a list of option codes and their descriptions, please look at the Telnet RFCs. The following are a few examples:

Command Event (Telnet Component)

Fired when a Telnet command comes from the Telnet server.

Syntax

type TCommandEvent = procedure (
  Sender: TObject;
  CommandCode: Integer
) of Object;

property OnCommand: TCommandEvent read FOnCommand write FOnCommand;

Remarks

Codes for Telnet commands and their meanings are defined in the Telnet RFCs. Here are some examples:

Connected Event (Telnet Component)

This event is fired immediately after a connection completes (or fails).

Syntax

type TConnectedEvent = procedure (
  Sender: TObject;
  StatusCode: Integer;
  const Description: String
) of Object;

property OnConnected: TConnectedEvent read FOnConnected write FOnConnected;

Remarks

If the connection is made normally, StatusCode is 0 and Description is 'OK'.

If the connection fails, StatusCode has the error code returned by the Transmission Control Protocol (TCP)/IP stack. Description contains a description of this code. The value of StatusCode is equal to the value of the error.

Please refer to the Error Codes section for more information.

ConnectionStatus Event (Telnet Component)

This event is fired to indicate changes in the connection state.

Syntax

type TConnectionStatusEvent = procedure (
  Sender: TObject;
  const ConnectionEvent: String;
  StatusCode: Integer;
  const Description: String
) of Object;

property OnConnectionStatus: TConnectionStatusEvent read FOnConnectionStatus write FOnConnectionStatus;

Remarks

The ConnectionStatus event is fired when the connection state changes: for example, completion of a firewall or proxy connection or completion of a security handshake.

The ConnectionEvent parameter indicates the type of connection event. Values may include the following:

DataIn Event (Telnet Component)

Fired when data is received from the remote host.

Syntax

type TDataInEvent = procedure (
  Sender: TObject;
  Text: String;
  TextB: TBytes
) of Object;

property OnDataIn: TDataInEvent read FOnDataIn write FOnDataIn;

Remarks

Trapping the DataIn event is your only chance to get the data coming from the other end of the connection. The incoming data is provided through the Text parameter.

Note: Events are not re-entrant. Performing time-consuming operations within this event will prevent it from firing again in a timely manner and may affect overall performance.

Disconnected Event (Telnet Component)

This event is fired when a connection is closed.

Syntax

type TDisconnectedEvent = procedure (
  Sender: TObject;
  StatusCode: Integer;
  const Description: String
) of Object;

property OnDisconnected: TDisconnectedEvent read FOnDisconnected write FOnDisconnected;

Remarks

If the connection is broken normally, StatusCode is 0 and Description is 'OK'.

If the connection is broken for any other reason, StatusCode has the error code returned by the Transmission Control Protocol (TCP/IP) subsystem. Description contains a description of this code. The value of StatusCode is equal to the value of the TCP/IP error.

Please refer to the Error Codes section for more information.

Do Event (Telnet Component)

Fired when a Telnet DO OPTION command comes from the Telnet server.

Syntax

type TDoEvent = procedure (
  Sender: TObject;
  OptionCode: Integer
) of Object;

property OnDo: TDoEvent read FOnDo write FOnDo;

Remarks

The OptionCode parameter identifies the option code. For a list of option codes and their descriptions, please look at the Telnet RFCs. The following are a few examples:

Dont Event (Telnet Component)

Fired when a Telnet DONT OPTION command comes from the Telnet server.

Syntax

type TDontEvent = procedure (
  Sender: TObject;
  OptionCode: Integer
) of Object;

property OnDont: TDontEvent read FOnDont write FOnDont;

Remarks

The OptionCode parameter identifies the option code. For a list of option codes and their descriptions, please look at the Telnet RFCs. The following are a few examples:

Error Event (Telnet Component)

Information about errors during data delivery.

Syntax

type TErrorEvent = procedure (
  Sender: TObject;
  ErrorCode: Integer;
  const Description: String
) of Object;

property OnError: TErrorEvent read FOnError write FOnError;

Remarks

The Error event is fired in case of exceptional conditions during message processing. Normally the component raises an exception.

The ErrorCode parameter contains an error code, and the Description parameter contains a textual description of the error. For a list of valid error codes and their descriptions, please refer to the Error Codes section.

ReadyToSend Event (Telnet Component)

Fired when the component is ready to send data.

Syntax

type TReadyToSendEvent = procedure (
  Sender: TObject
) of Object;

property OnReadyToSend: TReadyToSendEvent read FOnReadyToSend write FOnReadyToSend;

Remarks

The ReadyToSend event indicates that the underlying TCP/IP subsystem is ready to accept data after a failed DataToSend. The event is also fired immediately after a connection to the remote host is established.

SSLServerAuthentication Event (Telnet Component)

Fired after the server presents its certificate to the client.

Syntax

type TSSLServerAuthenticationEvent = procedure (
  Sender: TObject;
  CertEncoded: String;
  CertEncodedB: TBytes;
  const CertSubject: String;
  const CertIssuer: String;
  const Status: String;
  var Accept: Boolean
) of Object;

property OnSSLServerAuthentication: TSSLServerAuthenticationEvent read FOnSSLServerAuthentication write FOnSSLServerAuthentication;

Remarks

During this event, the client can decide whether or not to continue with the connection process. The Accept parameter is a recommendation on whether to continue or close the connection. This is just a suggestion: application software must use its own logic to determine whether or not to continue.

When Accept is False, Status shows why the verification failed (otherwise, Status contains the string OK). If it is decided to continue, you can override and accept the certificate by setting the Accept parameter to True.

SSLStatus Event (Telnet Component)

Shows the progress of the secure connection.

Syntax

type TSSLStatusEvent = procedure (
  Sender: TObject;
  const Message: String
) of Object;

property OnSSLStatus: TSSLStatusEvent read FOnSSLStatus write FOnSSLStatus;

Remarks

The event is fired for informational and logging purposes only. This event tracks the progress of the connection.

SubOption Event (Telnet Component)

Fired when a Telnet SubOption command comes from the Telnet server.

Syntax

type TSubOptionEvent = procedure (
  Sender: TObject;
  SubOption: String;
  SubOptionB: TBytes
) of Object;

property OnSubOption: TSubOptionEvent read FOnSubOption write FOnSubOption;

Remarks

The SubOption parameter contains the suboption data as sent by the other end. The enclosing suboption command codes are stripped away.

For a list of valid Telnet suboptions and their descriptions please look at the Telnet RFCs.

Will Event (Telnet Component)

Fired when a Telnet WILL OPTION command comes from the Telnet server.

Syntax

type TWillEvent = procedure (
  Sender: TObject;
  OptionCode: Integer
) of Object;

property OnWill: TWillEvent read FOnWill write FOnWill;

Remarks

For a list of option codes and their descriptions, please look at the Telnet RFCs. The following are a few examples:

Wont Event (Telnet Component)

Fired when a Telnet WONT OPTION command comes from the Telnet server.

Syntax

type TWontEvent = procedure (
  Sender: TObject;
  OptionCode: Integer
) of Object;

property OnWont: TWontEvent read FOnWont write FOnWont;

Remarks

The OptionCode parameter identifies the option code. For a list of option codes and their descriptions, please look at the Telnet RFCs. The following are a few examples:

Firewall Type

This is the firewall the component will connect through.

Remarks

When connecting through a firewall, this type is used to specify different properties of the firewall, such as the firewall Host and the FirewallType.

Fields

Constructors

constructor Create();

Config Settings (Telnet Component)

TCPClient Config Settings

SSL Config Settings

-----BEGIN CERTIFICATE-----
MIIEKzCCAxOgAwIBAgIRANTET4LIkxdH6P+CFIiHvTowDQYJKoZIhvcNAQELBQAw
...
eWHV5OW1K53o/atv59sOiW5K3crjFhsBOd5Q+cJJnU+SWinPKtANXMht+EDvYY2w
F0I1XhM+pKj7FjDr+XNj
-----END CERTIFICATE-----
\r \n
-----BEGIN CERTIFICATE-----
MIIEFjCCAv6gAwIBAgIQetu1SMxpnENAnnOz1P+PtTANBgkqhkiG9w0BAQUFADBp
..
d8q23djXZbVYiIfE9ebr4g3152BlVCHZ2GyPdjhIuLeH21VbT/dyEHHA
-----END CERTIFICATE-----

-----BEGIN CERTIFICATE-----
MIIEKzCCAxOgAwIBAgIRANTET4LIkxdH6P+CFIiHvTowDQYJKoZIhvcNAQELBQAw
...
eWHV5OW1K53o/atv59sOiW5K3crjFhsBOd5Q+cJJnU+SWinPKtANXMht+EDvYY2w
F0I1XhM+pKj7FjDr+XNj
-----END CERTIFICATE-----
\r \n
-----BEGIN CERTIFICATE-----
MIIEFjCCAv6gAwIBAgIQetu1SMxpnENAnnOz1P+PtTANBgkqhkiG9w0BAQUFADBp
..
d8q23djXZbVYiIfE9ebr4g3152BlVCHZ2GyPdjhIuLeH21VbT/dyEHHA
-----END CERTIFICATE-----

Socket Config Settings

Base Config Settings

Trappable Errors (Telnet Component)

Telnet Errors

The component may also return one of the following error codes, which are inherited from other components.

SSLClient Errors

SSL Errors

TCP/IP Errors