Options Property  
 

Gets and sets the options that are used in establishing a connection.

Syntax

object.Options [= value ]

Remarks

The Options property is an integer value which specifies one or more options. The value specified for this property will be used as the default options when connecting to the server. The property value is created by using a bitwise operator with one or more of the following values:

Value Constant Description
1 ftpOptionPassive This option specifies that the client should attempt to establish a passive connection to the server. This means that instead of the client opening a port on the local system and waiting for the server to establish a connection back to the client, the client will establish a second data connection to the server. This mode is recommended for most systems that are behind a NAT router or firewall.
2 ftpOptionFirewall This option specifies that the client should always use the host IP address to establish the data connection with the server, not the address returned by the server in response to the PASV command. This option may be necessary if the server is behind a router that performs Network Address Translation (NAT) and it returns an unreachable IP address for the data connection. If this option is specified, it will also enable passive mode data transfers.
4 ftpOptionNoAuth This option specifies that the server does not require authentication, or that it requires an alternate authentication method. When this option is used, the client connection is flagged as authenticated as soon as the connection to the server has been established. Note that using this option to bypass authentication may result in subsequent errors when attempting to retrieve a directory listing or transfer a file. It is recommended that you consult the technical reference documentation for the server to determine its specific authentication requirements.
8 ftpOptionKeepAlive This option specifies that the client should attempt to keep the connection with the server active for an extended period of time. It is important to note that regardless of this option, the server may still choose to disconnect client sessions that are holding the command channel open but are not performing file transfers.
16 ftpOptionNoAuthRSA This option specifies that RSA authentication should not be used with SSH-1 connections. This option is ignored with SSH-2 connections and should only be specified if required by the server. This option has no effect on standard or secure connections using SSL.
32 ftpOptionNoPwdNul This option specifies that the user password cannot be terminated with a null character. This option is ignored with SSH-2 connections and should only be specified if required by the server. This option has no effect on standard or secure connections using SSL.
64 ftpOptionNoRekey This option specifies that the client should never attempt a repeat key exchange with the server. Some SSH servers do not support rekeying the session, and this can cause the client to become non-responsive or abort the connection after being connected for an hour. This option has no effect on standard or secure connections using SSL.
128 ftpOptionCompatSID This compatibility option changes how the session ID is handled during public key authentication with older SSH servers. This option should only be specified when connecting to servers that use OpenSSH 2.2.0 or earlier versions. This option has no effect on standard or secure connections using SSL.
256 ftpOptionCompatHMAC This compatibility option changes how the HMAC authentication codes are generated. This option should only be specified when connecting to servers that use OpenSSH 2.2.0 or earlier versions. This option has no effect on standard or secure connections using SSL.
512 ftpOptionVirtualHost This option specifies that the server supports virtual hosting, where multiple domains are hosted by a server using the same external IP address. If this option is enabled, the client will send the HOST command to the server upon establishing a connection.
1024 ftpOptionVerify This option specifies that file transfers should be automatically verified after the transfer has completed. If the server supports the XMD5 command, the transfer will be verified by calculating an MD5 hash of the file contents. If the server does not support the XMD5 command, but does support the XCRC command, the transfer will be verified by calculating a CRC32 checksum of the file contents. If neither the XMD5 or XCRC commands are supported, the transfer is verified by comparing the size of the file. Automatic file verification is only performed for binary mode transfers because of the end-of-line conversion that may occur when text files are uploaded or downloaded.
2048 ftpOptionTrustedSite This option specifies that the server is trusted. The server certificate will not be validated and the connection will always be permitted. This option only affects connections using either the SSL or TLS protocols.
4096 ftpOptionSecure This option specifies that the client should attempt to establish a secure connection with the server. Note that the server must support secure connections using either the SSL or TLS protocol.
8192 ftpOptionSecureExplicit This option specifies that the client should use the AUTH TLS-P command to negotiate an explicit secure connection. Some servers may only require this when connecting to the server on ports other than 990.
16384 ftpOptionSecureShell This option specifies that the client should use the Secure Shell (SSH) protocol to establish the connection. This option will automatically be selected if the connection is established using port 22, the default port for SSH, and is only required if the server is configured to use a non-standard port number.
65536 ftpOptionTunnel This option specifies that a tunneled TCP connection and/or port-forwarding is being used to establish the connection to the server. This changes the behavior of the client with regards to internal checks of the destination IP address and remote port number, default feature selection and how the connection is established. This option also forces all connections to be outbound and enables the firewall compatibility features in the client.

Note that setting the ftpOptionPassive option is the same as setting the Passive property to True.

If the ftpOptionSecureExplicit option is specified, the client will first send an AUTH TLS command to the server. If the server does not accept this command, it will then send an AUTH SSL command. If both commands are rejected by the server, an explicit SSL session cannot be established. By default, both the command and data channels will be encrypted when a secure connection is established. To change this, set the ChannelMode property.

Data Type

Integer (Int32)

Example

'
' The Ipswitch WS_FTP server accepts the AUTH command to establish
' an explicit SSL session on the default FTP port
'

FtpClient1.Options = ftpOptionSecureExplicit
nError = FtpClient1.Connect(strHostName)

'
' When the GlobalSCAPE Secure FTP server is configured in implicit
' authorization mode, it negotiates a secure session as soon as the
' connection is established and does not require a command
'

FtpClient1.Options = ftpOptionSecure
nError = FtpClient1.Connect(strHostName)

See Also

Priority Property, Secure Property, Connect Method