TCPServer Control

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The TCPServer Control is a generic Transmission Control Protocol (TCP) server control based on an asynchronous, event-driven architecture. It is designed to balance the load between connections for a fast, powerful server.

Syntax

TCPServer

Remarks

The TCPServer Control supports both plaintext and Secure Sockets Layer/Transport Layer Security (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 SSLCert properties are used to select a certificate for the server. Note: A valid certificate MUST be selected before the server can function.

TCPServer is the server complement of TCPClient, which is used to create client applications. They share a common design philosophy and interface. We expect you will find TCPServer as easy to use as TCPClient.

By default, each instance of TCPServer can handle up to 1,000 simultaneous incoming connections. This number may be increased up to 100,000 or decreased to a lower value by using the MaxConnections configuration setting.

The connections are identified by a ConnectionId, an Id generated by the component to identify each connection. This Id is unique to each connection. TCPServer's events also have ConnectionId as a parameter to identify the connection they relate to.

Our main goal in designing TCPServer was to make it easy to use without sacrificing performance. The control has a minimum of properties, and six events: ConnectionRequest, Connected, DataIn, Disconnected, ReadyToSend, and Error.

TCPServer can start to listen on a port by setting the Listening property to True. When a remote host asks for a connection, the ConnectionRequest event is fired. At that point, the connection can either be accepted or rejected. If the connection is accepted, a ConnectionId is assigned, and communication can start. From this point on, the operation is very similar to TCPClient. Data are sent by assigning the data string to the DataToSend property. The address and port of the incoming connection can be found by querying the RemoteHost and RemotePort properties.

Note: Server components are designed to process events as they occur. To ensure that events are processed in a timely manner, DoEvents should be called in a loop after the server is started.

Property List

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

Method List

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

Event List

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

Config Settings

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

ConnectionBacklog Property (TCPServer Control)

This property includes the maximum number of pending connections maintained by the Transmission Control Protocol (TCP)/IP subsystem.

Syntax

tcpservercontrol.ConnectionBacklog[=integer]

Default Value

5

Remarks

This property contains the maximum number of pending connections maintained by the TCP/IP subsystem. This value reflects the SOMAXCONN option for the main listening socket. The default value for most systems is 5. You may set this property to a larger value if the server is expected to receive a large number of connections, and queuing them is desirable.

This property is not available at design time.

Data Type

Integer

ConnectionCount Property (TCPServer Control)

The number of records in the arrays.

Syntax

tcpservercontrol.ConnectionCount

Default Value

0

Remarks

This property controls the size of the following arrays:

• AcceptData
• BytesSent
• Connected
• ConnectionId
• DataToSend
• EOL
• IdleTimeout
• LocalAddress
• ReadyToSend
• RecordLength
• RemoteHost
• RemotePort
• SingleLineMode
• SSLCertEncoded
• SSLCertStore
• SSLCertStorePassword
• SSLCertStoreType
• SSLCertSubject
• Timeout
• UserData

The array indices start at 0 and end at ConnectionCount - 1.

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

Data Type

Integer

AcceptData Property (TCPServer Control)

Setting this property to false temporarily disables data reception (and the DataIn event) for the connection.

Syntax

tcpservercontrol.AcceptData(ConnectionId)[=boolean]

Default Value

True

Remarks

Setting this property to false temporarily disables data reception (and the DataIn event) for the connection. Setting this to true re-enables data reception.

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

The ConnectionId parameter specifies the index of the item in the array. The size of the array is controlled by the ConnectionCount property.

This property is not available at design time.

Data Type

Boolean

BytesSent Property (TCPServer Control)

This property shows how many bytes were sent after the last assignment to DataToSend .

Syntax

tcpservercontrol.BytesSent(ConnectionId)

Default Value

0

Remarks

This property shows how many bytes were sent after the last assignment to DataToSend. Please check DataToSend for more information.

Note: This property will always return 0 when the control is operating in the synchronous mode (i.e., the Timeout property is set to a positive value).

The ConnectionId parameter specifies the index of the item in the array. The size of the array is controlled by the ConnectionCount property.

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

Data Type

Integer

Connected Property (TCPServer Control)

This property is used to disconnect individual connections or to show their status.

Syntax

tcpservercontrol.Connected(ConnectionId)[=boolean]

Default Value

False

Remarks

This property is used to disconnect individual connections or to show their status.

The Connected property may be set to to close the connection.

Connected also shows the status of a particular connection (connected/disconnected).

How and when the connection is closed is controlled by the Linger property. Please refer to its description for more information.

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

The ConnectionId parameter specifies the index of the item in the array. The size of the array is controlled by the ConnectionCount property.

This property is not available at design time.

Data Type

Boolean

ConnectionId Property (TCPServer Control)

This property contains an identifier generated by the control to identify each connection.

Syntax

tcpservercontrol.ConnectionId(ConnectionId)

Default Value

""

Remarks

This property contains an identifier generated by the control to identify each connection. This identifier is unique to this connection.

The ConnectionId parameter specifies the index of the item in the array. The size of the array is controlled by the ConnectionCount property.

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

Data Type

String

DataToSend Property (TCPServer Control)

This property contains a string of data to be sent to the remote host.

Syntax

tcpservercontrol.DataToSend(ConnectionId)[=string]

Default Value

""

Remarks

This property contains a string of data to be sent to the remote host. It is a write-only property.

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

When Timeout is set to 0, the control will behave asynchronously. 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 fails with error 25036: "[10035] Operation would block" (WSAEWOULDBLOCK). You can trap this error, 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.

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

The ConnectionId parameter specifies the index of the item in the array. The size of the array is controlled by the ConnectionCount property.

To read or write binary data to the property, a Variant (Byte Array) version is provided in .DataToSendB.

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

Data Type

Binary String

EOL Property (TCPServer Control)

The EOL property is used to define boundaries in the input stream using the value of the property.

Syntax

tcpservercontrol.EOL(ConnectionId)[=string]

Default Value

""

Remarks

The EOL property is used to define boundaries in the input stream using the value of the property.

The EOL property is especially useful with ASCII files. By setting it to CRLF (Chr$(13) & Chr$(10)) , the incoming ASCII text stream can be split into lines. In this case, one event is fired for each line received (as well as in packet boundaries). The CRLF (Chr$(13) & Chr$(10)) . bytes are discarded.

The EOL property is a binary string. This means that it can be more than one byte long, and it can contain NULL bytes.

The ConnectionId parameter specifies the index of the item in the array. The size of the array is controlled by the ConnectionCount property.

To read or write binary data to the property, a Variant (Byte Array) version is provided in .EOLB.

This property is not available at design time.

Data Type

Binary String

IdleTimeout Property (TCPServer Control)

This property contains the idle timeout for this connection.

Syntax

tcpservercontrol.IdleTimeout(ConnectionId)[=integer]

Default Value

0

Remarks

This property contains the idle timeout for this connection. This property is similar to DefaultIdleTimeout but may be set on a per-connection basis to override DefaultIdleTimeout. This property specifies the idle timeout (in seconds) for the connected client. When set to a positive value, the control will disconnect idle clients after the specified timeout.

This applies only to clients that have not sent to received data within the specified number of seconds.

If set to 0 (default), no idle timeout is applied.

Note: DoEvents must be called for the control to check existing connections.

The ConnectionId parameter specifies the index of the item in the array. The size of the array is controlled by the ConnectionCount property.

This property is not available at design time.

Data Type

Integer

LocalAddress Property (TCPServer Control)

This property shows the IP address of the interface through which the connection is passing.

Syntax

tcpservercontrol.LocalAddress(ConnectionId)

Default Value

""

Remarks

This property shows the IP address of the interface through which the connection is passing.

LocalAddress is important for multihomed hosts so that it can be used to find the particular network interface through which an individual connection is going.

The ConnectionId parameter specifies the index of the item in the array. The size of the array is controlled by the ConnectionCount property.

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

Data Type

String

ReadyToSend Property (TCPServer Control)

This indicates whether the control is ready to send data.

Syntax

tcpservercontrol.ReadyToSend(ConnectionId)

Default Value

False

Remarks

This indicates whether the control is ready to send data.

This property indicates that the underlying TCP/IP subsystem is ready to accept data. This is True after a client connects but will become False after a failed DataToSend.

After a failed DataToSend, the ReadyToSend event will fire and this property will be True when data can be sent again.

The ConnectionId parameter specifies the index of the item in the array. The size of the array is controlled by the ConnectionCount property.

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

Data Type

Boolean

RecordLength Property (TCPServer Control)

If set to a positive value, this setting defines the length of the data records to be received.

Syntax

tcpservercontrol.RecordLength(ConnectionId)[=integer]

Default Value

0

Remarks

If set to a positive value, this setting defines the length of the data records to be received. The control will accumulate data until RecordLength is reached and only then will fire the DataIn event with the data of length RecordLength. This allows data to be received as records of known length. This value can be changed at any time, including within the DataIn event.

A value of 0 (default) means this setting is not used.

Note: It is recommended to use the ChangeRecordLength method instead of setting this property.

The ConnectionId parameter specifies the index of the item in the array. The size of the array is controlled by the ConnectionCount property.

This property is not available at design time.

Data Type

Integer

RemoteHost Property (TCPServer Control)

This property shows the IP address of the remote host through which the connection is coming.

Syntax

tcpservercontrol.RemoteHost(ConnectionId)

Default Value

""

Remarks

This property shows the IP address of the remote host through which the connection is coming.

The connection must be valid or an error will be fired.

If the control 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.

The ConnectionId parameter specifies the index of the item in the array. The size of the array is controlled by the ConnectionCount property.

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

Data Type

String

RemotePort Property (TCPServer Control)

This property shows the Transmission Control Protocol (TCP) port on the remote host through which the connection is coming.

Syntax

tcpservercontrol.RemotePort(ConnectionId)

Default Value

0

Remarks

This property shows the Transmission Control Protocol (TCP) port on the remote host through which the connection is coming.

The connection must be valid or an error will be fired.

The ConnectionId parameter specifies the index of the item in the array. The size of the array is controlled by the ConnectionCount property.

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

Data Type

Integer

SingleLineMode Property (TCPServer Control)

This property shows the special mode for line-oriented protocols.

Syntax

tcpservercontrol.SingleLineMode(ConnectionId)[=boolean]

Default Value

False

Remarks

This property shows the special mode for line-oriented protocols. When SingleLineMode is True, the control treats the incoming data stream as lines separated by carriage return (CR), line feed (LF), or CRLF. The EOL property is ignored.

The ConnectionId parameter specifies the index of the item in the array. The size of the array is controlled by the ConnectionCount property.

This property is not available at design time.

Data Type

Boolean

Timeout Property (TCPServer Control)

This property specifies a timeout for the control.

Syntax

tcpservercontrol.Timeout(ConnectionId)[=integer]

Default Value

0

Remarks

This property specifies a timeout for the control.

If the Timeout property is set to 0, all operations return immediately, potentially failing with a WOULDBLOCK error if data cannot be sent immediately.

If Timeout is set to a positive value, data is sent in a blocking manner and the control will wait for the operation to complete before returning control. The control will handle any potential WOULDBLOCK errors internally and automatically retry the operation for a maximum of Timeout seconds.

The control 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 control fails with an error.

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).

The ConnectionId parameter specifies the index of the item in the array. The size of the array is controlled by the ConnectionCount property.

This property is not available at design time.

Data Type

Integer

UserData Property (TCPServer Control)

The UserData property holds connection-specific user-specified data.

Syntax

tcpservercontrol.UserData(ConnectionId)[=string]

Default Value

""

Remarks

The UserData property holds connection-specific user-specified data.

User-specified data may be set or retrieved at any point while the connection is valid. This provides a simple way to associate arbitrary data with a specific connection.

The ConnectionId parameter specifies the index of the item in the array. The size of the array is controlled by the ConnectionCount property.

To read or write binary data to the property, a Variant (Byte Array) version is provided in .UserDataB.

This property is not available at design time.

Data Type

Binary String

DefaultEOL Property (TCPServer Control)

This property includes a default end-of-line (EOL) value to be used by incoming connections.

Syntax

tcpservercontrol.DefaultEOL[=string]

Default Value

""

Remarks

This property contains a default end-of-line (EOL) value to be used by incoming connections. Once the control accepts and establishes an inbound connection, it will set that connection's EOL to the value in this property. By default, this value is empty (""), meaning that data will be fired as it is received.

To read or write binary data to the property, a Variant (Byte Array) version is provided in .DefaultEOLB.

Data Type

Binary String

DefaultIdleTimeout Property (TCPServer Control)

This property includes the default idle timeout for inactive clients.

Syntax

tcpservercontrol.DefaultIdleTimeout[=integer]

Default Value

0

Remarks

This property specifies the idle timeout (in seconds) for clients. When set to a positive value, the control will disconnect idle clients after the specified timeout.

This applies only to clients that have not sent or received data within DefaultIdleTimeout seconds.

If set to 0 (default), no idle timeout is applied.

Note: DoEvents must be called for the control to check existing connections.

Data Type

Integer

DefaultMaxLineLength Property (TCPServer Control)

The property includes the default maximum line length value for inbound connections.

Syntax

tcpservercontrol.DefaultMaxLineLength[=integer]

Default Value

2048

Remarks

This property controls the default size of an internal buffer that holds received data while waiting for an end-of-line (EOL) string.

The minimum value for this property is 256 bytes. The default value is 2048 bytes.

Data Type

Integer

DefaultSingleLineMode Property (TCPServer Control)

This property tells the control whether or not to treat new connections as line oriented.

Syntax

tcpservercontrol.DefaultSingleLineMode[=boolean]

Default Value

False

Remarks

This property instructs the component whether or not to treat newly established connections as line-oriented protocols. If this value is True, newly accepted connections will read the incoming data stream as lines separated by a carriage return line feed (CRLF), carriage return (CR), or line feed (LF) and will ignore the end of lines (EOLs).

Data Type

Boolean

DefaultTimeout Property (TCPServer Control)

This property includes an initial timeout value to be used by incoming connections.

Syntax

tcpservercontrol.DefaultTimeout[=integer]

Default Value

0

Remarks

This property is used by the control to set the operational timeout value of all inbound connections once they are established.

By default, the timeout is 0, meaning that all inbound connections will behave asynchronously.

Data Type

Integer

KeepAlive Property (TCPServer Control)

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

Syntax

tcpservercontrol.KeepAlive[=boolean]

Default Value

False

Remarks

This property enables the SO_KEEPALIVE option on the incoming connections. 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.

This property is shared among incoming connections. When the property is set, the corresponding value is set for incoming connections as they are accepted. Existing connections are not modified.

Data Type

Boolean

Linger Property (TCPServer Control)

When set to True, connections are terminated gracefully.

Syntax

tcpservercontrol.Linger[=boolean]

Default Value

True

Remarks

This property controls how a connection is closed. The default is True. In this case, the connection is closed only after all the data are sent. Setting it to False forces an abrupt (hard) disconnection. Any data that were in the sending queue may be lost.

The default behavior (which is also the default mode for stream sockets) might result in an indefinite delay in closing the connection. Although the control returns control immediately, the system might indefinitely hold system resources until all pending data are sent (even after your application closes). This means that valuable system resources might be wasted.

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

This property is shared among incoming connections. When the property is set, the corresponding value is set for incoming connections as they are accepted. Existing connections are not modified.

Data Type

Boolean

Listening Property (TCPServer Control)

If set to True, the control accepts incoming connections on LocalPort.

Syntax

tcpservercontrol.Listening[=boolean]

Default Value

False

Remarks

This property indicates whether the control is listening for connections on the port specified by the LocalPort property.

Note: Use the StartListening and StopListening methods to control whether the control is listening.

This property is not available at design time.

Data Type

Boolean

LocalHost Property (TCPServer Control)

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

Syntax

tcpservercontrol.LocalHost[=string]

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 control initiate connections (or accept in the case of server controls) only through that interface.

If the control 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.

Data Type

String

LocalPort Property (TCPServer Control)

This property includes the Transmission Control Protocol (TCP) port in the local host where the control listens.

Syntax

tcpservercontrol.LocalPort[=integer]

Default Value

0

Remarks

This property must be set before the control can start listening. If its value is 0, then the TCP/IP subsystem picks a port number at random. The port number can be found by checking the value of this property after the control is listening (i.e., after successfully assigning True to the Listening property).

The service port is not shared among servers so two controls cannot be listening on the same port at the same time.

Data Type

Integer

SSLAuthenticateClients Property (TCPServer Control)

If set to True, the server asks the client(s) for a certificate.

Syntax

tcpservercontrol.SSLAuthenticateClients[=boolean]

Default Value

False

Remarks

This property is used in conjunction with the SSLClientAuthentication event. Please refer to the documentation of the SSLClientAuthentication event for details.

Data Type

Boolean

SSLCertEncoded Property (TCPServer Control)

This is the certificate (PEM/Base64 encoded).

Syntax

tcpservercontrol.SSLCertEncoded[=string]

Default Value

""

Remarks

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

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

To read or write binary data to the property, a Variant (Byte Array) version is provided in .SSLCertEncodedB.

This property is not available at design time.

Data Type

Binary String

SSLCertStore Property (TCPServer Control)

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

Syntax

tcpservercontrol.SSLCertStore[=string]

Default Value

"MY"

Remarks

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

The SSLCertStoreType property denotes the type of the certificate store specified by SSLCertStore. If the store is password protected, specify the password in SSLCertStorePassword.

SSLCertStore is used in conjunction with the SSLCertSubject property to specify client certificates. If SSLCertStore has a value, and SSLCertSubject or SSLCertEncoded is set, a search for a certificate is initiated. Please see the SSLCertSubject 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).

To read or write binary data to the property, a Variant (Byte Array) version is provided in .SSLCertStoreB.

Data Type

Binary String

SSLCertStorePassword Property (TCPServer Control)

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

Syntax

tcpservercontrol.SSLCertStorePassword[=string]

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.

Data Type

String

SSLCertStoreType Property (TCPServer Control)

This is the type of certificate store for this certificate.

Syntax

tcpservercontrol.SSLCertStoreType[=integer]

Possible Values

cstUser(0), 
cstMachine(1), 
cstPFXFile(2), 
cstPFXBlob(3), 
cstJKSFile(4), 
cstJKSBlob(5), 
cstPEMKeyFile(6), 
cstPEMKeyBlob(7), 
cstPublicKeyFile(8), 
cstPublicKeyBlob(9), 
cstSSHPublicKeyBlob(10), 
cstP7BFile(11), 
cstP7BBlob(12), 
cstSSHPublicKeyFile(13), 
cstPPKFile(14), 
cstPPKBlob(15), 
cstXMLFile(16), 
cstXMLBlob(17), 
cstJWKFile(18), 
cstJWKBlob(19), 
cstSecurityKey(20), 
cstBCFKSFile(21), 
cstBCFKSBlob(22), 
cstPKCS11(23), 
cstAuto(99)

Default Value

0

Remarks

This is the type of certificate store for this certificate.

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

Data Type

Integer

SSLCertSubject Property (TCPServer Control)

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

Syntax

tcpservercontrol.SSLCertSubject[=string]

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.

Data Type

String

SSLEnabled Property (TCPServer Control)

Whether TLS/SSL is enabled.

Syntax

tcpservercontrol.SSLEnabled[=boolean]

Default Value

False

Remarks

This setting specifies whether TLS/SSL is enabled in the control. When False (default) the control operates in plaintext mode. When True TLS/SSL is enabled.

TLS/SSL may also be enabled by setting SSLStartMode. Setting SSLStartMode will automatically update this property value.

This property is not available at design time.

Data Type

Boolean

SSLProvider Property (TCPServer Control)

This specifies the SSL/TLS implementation to use.

Syntax

tcpservercontrol.SSLProvider[=integer]

Possible Values

sslpAutomatic(0), 
sslpPlatform(1), 
sslpInternal(2)

Default Value

0

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 control 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 control will select a provider depending on the current platform.

When Automatic is selected the platform implementation is used by default. When TLS 1.3 is enabled via SSLEnabledProtocols the internal implementation is used.

Data Type

Integer

SSLStartMode Property (TCPServer Control)

Determines how the control starts the SSL negotiation.

Syntax

tcpservercontrol.SSLStartMode[=integer]

Possible Values

sslAutomatic(0), 
sslImplicit(1), 
sslExplicit(2), 
sslNone(3)

Default Value

3

Remarks

The SSLStartMode property may have one of the following values:

Data Type

Integer

ChangeRecordLength Method (TCPServer Control)

This method changes the length of received data records.

Syntax

tcpservercontrol.ChangeRecordLength ConnectionId, RecordLength

Remarks

This method defines the length of data records to be received (in bytes) for the specified ConnectionId.

If RecordLength is set to a positive value, the control will accumulate data until RecordLength bytes of data are received and only then will fire the DataIn event with data of the specified length RecordLength. This allows data to be received as records of known length. This method can be called at any time to change the record length, including within the DataIn event.

A value of 0 (default) means this functionality is not used.

Config Method (TCPServer Control)

Sets or retrieves a configuration setting.

Syntax

tcpservercontrol.Config ConfigurationString

Remarks

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

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the control, 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.

Disconnect Method (TCPServer Control)

This method disconnects the specified client.

Syntax

tcpservercontrol.Disconnect ConnectionId

Remarks

Calling this method will disconnect the client specified by the ConnectionId parameter.

DoEvents Method (TCPServer Control)

Processes events from the internal message queue.

Syntax

tcpservercontrol.DoEvents 

Remarks

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

Interrupt Method (TCPServer Control)

This method interrupts a synchronous send to the remote host.

Syntax

tcpservercontrol.Interrupt ConnectionId

Remarks

This property is called using the Connection Id if you wish to interrupt a connection and stop a file from uploading without disconnecting the client connected to the control. If you use SendFile to upload a file, the control will run synchronously on that Connection Id until it is completed.

PauseData Method (TCPServer Control)

This method pauses data reception.

Syntax

tcpservercontrol.PauseData ConnectionId

Remarks

This method pauses data reception for the connection identified by ConnectionId when called. While data reception is paused, the DataIn event will not fire for the specified connection. Call ProcessData to reenable data reception.

ProcessData Method (TCPServer Control)

This method reenables data reception after a call to PauseData .

Syntax

tcpservercontrol.ProcessData ConnectionId

Remarks

This method reenables data reception for the connection identified by ConnectionId after a previous call to PauseData. When PauseData is called, the DataIn event will not fire for the specified connection. 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 (TCPServer Control)

Reset the control.

Syntax

tcpservercontrol.Reset 

Remarks

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

Send Method (TCPServer Control)

This method sends binary data to the specified client.

Syntax

tcpservercontrol.Send ConnectionId, Text

Remarks

This method sends binary data to the client identified by ConnectionId. To send text, use the SendText method instead.

When WSConnectionTimeout is set to 0, the control will behave asynchronously. 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 fails with error 25036: "[10035] Operation would block" (WSAEWOULDBLOCK). You can trap this error, 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.

SendBytes Method (TCPServer Control)

This method sends binary data to the specified client.

Syntax

tcpservercontrol.SendBytes ConnectionId, Data

Remarks

This method sends binary data to the client identified by ConnectionId. To send text, use the SendText method instead.

When WSConnectionTimeout is set to 0, the control will behave asynchronously. 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 fails with error 25036: "[10035] Operation would block" (WSAEWOULDBLOCK). You can trap this error, 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.

SendFile Method (TCPServer Control)

This method sends the file to the remote host.

Syntax

tcpservercontrol.SendFile ConnectionId, FileName

Remarks

This method sends the file to the client specified by the ConnectionId.

SendLine Method (TCPServer Control)

This method sends a string followed by a new line.

Syntax

tcpservercontrol.SendLine ConnectionId, Text

Remarks

This method is used to send data with line-oriented protocols. The line is followed by CRLF (Chr$(13) & Chr$(10)) .

Please refer to the GetLine method and SingleLineMode property for more information.

SendText Method (TCPServer Control)

This method sends text to the specified client.

Syntax

tcpservercontrol.SendText ConnectionId, Text

Remarks

This method sends text to the client identified by ConnectionId. To send binary data, use the SendBytes method instead.

When WSConnectionTimeout is set to 0, the control will behave asynchronously. 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 fails with error 25036: "[10035] Operation would block" (WSAEWOULDBLOCK). You can trap this error, 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.

Shutdown Method (TCPServer Control)

This method shuts down the server.

Syntax

tcpservercontrol.Shutdown 

Remarks

This method shuts down the server. Calling this method is equivalent to calling StopListening and then breaking every client connection by calling Disconnect.

StartListening Method (TCPServer Control)

This method starts listening for incoming connections.

Syntax

tcpservercontrol.StartListening 

Remarks

This method begins listening for incoming connections on the port specified by LocalPort. Once listening, events will fire as new clients connect and data are transferred.

To stop listening for new connections, call StopListening. To stop listening for new connections and to disconnect all existing clients, call Shutdown.

StartSSL Method (TCPServer Control)

This method starts the Secure Sockets Layer (SSL) negotiation on a connection.

Syntax

tcpservercontrol.StartSSL ConnectionId

Remarks

This method is used to start the SSL negotiation on a plaintext connection. Please refer to the SSLStartMode property for more information.

Note: The Connected event will fire again after the SSL negotiation is complete.

StopListening Method (TCPServer Control)

This method stops listening for new connections.

Syntax

tcpservercontrol.StopListening 

Remarks

This method stops listening for new connections. After being called, any new connection attempts will be rejected. Calling this method does not disconnect existing connections.

To stop listening and to disconnect all existing clients, call Shutdown instead.

Connected Event (TCPServer Control)

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

Syntax

Sub tcpservercontrol_Connected(ConnectionId As Integer, StatusCode As Integer, Description As String)

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 system. Description contains a description of this code. The value of StatusCode is equal to the value of the system error. The corresponding Visual Basic error code can be obtained by adding 15001 to this value.

Please refer to the Error Codes section for more information.

ConnectionRequest Event (TCPServer Control)

This event is fired when a request for connection comes from a remote host.

Syntax

Sub tcpservercontrol_ConnectionRequest(Address As String, Port As Integer, Accept As Boolean)

Remarks

This event indicates an incoming connection. The connection is accepted by default. Address and Port will contain information about the remote host requesting the inbound connection. If you want to refuse it, you can set the Accept parameter to False.

DataIn Event (TCPServer Control)

This event is fired when data come in.

Syntax

Sub tcpservercontrol_DataIn(ConnectionId As Integer, Text As String, EOL As Boolean)

Remarks

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

EOL indicates whether or not the EOL string was found at the end of Text. If the EOL string was found, then EOL is True.

If Text is part of the data portion of length larger than either DefaultMaxLineLength or with no EOL strings in it, then EOL is False. Please note that this means that one or more DataIn events with EOL set to False can be received during a connection.

If the EOL property is "" (empty string), then EOL can be disregarded (it is always True).

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 (TCPServer Control)

This event is fired when a connection is closed.

Syntax

Sub tcpservercontrol_Disconnected(ConnectionId As Integer, StatusCode As Integer, Description As String)

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 system. Description contains a description of this code. The value of StatusCode is equal to the value of the system error. The corresponding Visual Basic error code can be obtained by adding 15001 to this value.

Please refer to the Error Codes section for more information.

Error Event (TCPServer Control)

This event fires information about errors during data delivery.

Syntax

Sub tcpservercontrol_Error(ConnectionId As Integer, ErrorCode As Integer, Description As String)

Remarks

The Error event is fired in case of exceptional conditions during message processing. Normally, the control fails with an error.

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

ConnectionId indicates the connection for which the error is applicable.

ReadyToSend Event (TCPServer Control)

This event is fired when the control is ready to send data.

Syntax

Sub tcpservercontrol_ReadyToSend(ConnectionId As Integer)

Remarks

The ReadyToSend event indicates that the underlying Transmission Control Protocol (TCP)/IP subsystem is ready to accept data after a failed DataToSend. This event is also fired immediately after a connection is established.

SSLClientAuthentication Event (TCPServer Control)

This event is fired when the client presents its credentials to the server.

Syntax

Sub tcpservercontrol_SSLClientAuthentication(ConnectionId As Integer, CertEncoded As String, CertSubject As String, CertIssuer As String, Status As String, Accept As Boolean)

Remarks

This event enables the server to decide whether or not to continue. The Accept parameter is a recommendation on whether to continue or to 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").

SSLConnectionRequest Event (TCPServer Control)

This event fires when a Secure Sockets Layer (SSL) connection is requested.

Syntax

Sub tcpservercontrol_SSLConnectionRequest(ConnectionId As Integer, SupportedCipherSuites As String, SupportedSignatureAlgs As String, CertStoreType As Integer, CertStore As String, CertPassword As String, CertSubject As String)

Remarks

This event fires when an SSL connection is requested and SSLProvider is set to Internal. This event provides an opportunity to select an alternative certificate to the connecting client. This event does not fire when SSLProvider is set to Platform.

This event allows the control to be configured to use both RSA and ECDSA certificates depending on the connecting client's capabilities.

ConnectionId is the connection Id of the client requesting the connection.

SupportedCipherSuites is a comma-separated list of cipher suites that the client supports.

SupportedSignatureAlgs is a comma-separated list of certificate signature algorithms that the client supports.

CertStoreType is the store type of the alternate certificate to use for this connection. The control supports both public and private keys in a variety of formats. When the cstAuto value is used, the control will automatically determine the type. This property can take one of the following values:

CertStore is the store name or location of the alternate certificate to use for this connection.

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).

CertPassword is the password of the certificate store containing the alternate certificate to use for this connection.

CertSubject is the subject of the alternate certificate to use for this connection.

The special value * matches any subject and will select the first certificate in the 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.

SSLStatus Event (TCPServer Control)

This event is fired to show the progress of the secure connection.

Syntax

Sub tcpservercontrol_SSLStatus(ConnectionId As Integer, Message As String)

Remarks

The event is fired for informational and logging purposes only. It is used to track the progress of the connection.

Config Settings (TCPServer Control)

TCPServer 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-----

Base Config Settings

Trappable Errors (TCPServer Control)

TCPServer Errors

SSL Errors

TCP/IP Errors