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Establish a connection with a server.
Syntax
object.Connect( [RemoteAddress],
[RemotePort], [Protocol], [Timeout],
[Options], [LocalAddress], [LocalPort] )
Parameters
- RemoteAddress
- An optional string value that specifies the host name or IP address
of the server. If this parameter is omitted, it
defaults to the value of the HostAddress property if it is
defined; otherwise, it defaults to the value of the HostName
property.
- RemotePort
- An optional integer value that specifies the port number that
the server is using to listen for connections. If this parameter is
omitted, the RemotePort property will be used to
determine the default value.
- Protocol
- An an optional integer value that specifies the protocol that
should be used when establishing the connection. If this parameter
is omitted, the
Protocol property will be used to determine the default value. It may be one of
the following values:
| Value |
Description |
| swProtocolTcp |
The connection will use the Transmission Control Protocol.
This protocol provides a reliable means of communication between
two computers using a client/server architecture. The data is
exchanged as a stream of bytes, with the protocol ensuring that
the data arrives in the same byte order that it was sent,
without duplication or missing data. This protocol is designed
for accuracy and not speed, therefore TCP can sometimes incur
relatively long delays while waiting for out-of-order packets
and the retransmission of data which can make it unsuitable for
some applications such as streaming video or audio. |
| swProtocolUdp |
The connection will use the User Datagram Protocol. This is
a stateless, peer-to-peer message oriented protocol, with the data
sent in discrete packets. UDP is a simpler network protocol that
does not have the inherent reliability of TCP, but it has less
overhead and is ideal for real-time applications where a dropped
packet is preferable to the delay of waiting for a packet to be
acknowledged or retransmitted. It also supports the broadcasting
of datagrams over local networks, and is commonly used by
services that must exchange a relatively small amount of data
with a large number of clients. |
- Timeout
- An optional integer value that specifies the amount of time until
a blocking operation fails. If this parameter is omitted, the
Timeout property will be used to determine the default value.
- Options
- An optional integer value that specifies one or more socket
options which are to be used when establishing the connection. The
value is created by combining the options using a bitwise Or
operator. Note that if this argument is specified, it will override
any property values that are related to that option.
| Value |
Description |
| swOptionBroadcast |
This option specifies that broadcasting should be enabled
for datagrams. This option is invalid for stream sockets. |
| swOptionDontRoute |
This option specifies default routing should not be used.
This option should not be specified unless absolutely necessary. |
| swOptionKeepAlive |
This option specifies that packets are to be sent to the
remote system when no data is being exchanged to keep the
connection active. This is only valid for stream sockets. |
| &H10 |
swOptionNoDelay |
This option disables the Nagle algorithm. By default, small
amounts of data written to the socket are buffered, increasing
efficiency and reducing network congestion. However, this
buffering can negatively impact the responsiveness of certain
applications. This option disables this buffering and
immediately sends data packets as they are written to the
socket. |
| &H20 |
swOptionInLine |
This option specifies that out-of-band data should be
received inline with the standard data stream. This option is
only valid for stream sockets. |
| &H800 |
swOptionTrustedSite |
This option specifies 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 TLS protocol. |
| &H1000 |
swOptionSecure |
This option specifies that a secure connection should be
established with the remote host. The specific version of TLS
can be specified by setting the SecureProtocol
property. By default, the connection will use TLS 1.2
and the strongest cipher suites available. Older versions
of Windows prior to Windows 7 and Windows Server 2008 R2 only
support TLS 1.0 and secure connections will automatically
downgrade on those platforms. |
| &H8000 |
swOptionSecureFallback |
This option specifies the client should permit the use
of less secure cipher suites for compatibility with legacy
servers. If this option is specified, the client will allow
connections using TLS 1.0 and cipher suites that use RC4, MD5
and SHA1. |
| &H40000 |
swOptionPreferIPv6 |
This option specifies the client should prefer the use of
IPv6 if the server hostname can be resolved to both an IPv6 and
IPv4 address. This option is ignored if the local system does
not have IPv6 enabled, or when the hostname can only be resolved
to an IPv4 address. If the server hostname can only be resolved
to an IPv6 address, the client will attempt to establish a
connection using IPv6 regardless if this option has been
specified. |
- LocalAddress
- An optional string value that specifies the local IP address of
the network adapter that the control should use when establishing
the connection. If this parameter is omitted, the control will bind
to any suitable adapter on the local system. It is recommended that
you omit this parameter when establishing a TCP connection unless
you fully understand the implications of binding the socket to a
specific local address.
- LocalPort
- An optional integer value that specifies the local port number
that the control should use when establishing the connection. If
this argument is not specified, an appropriate local port number
will be automatically allocated for the connection. It is
recommended that you omit this parameter when establishing a TCP
connection unless you fully understand the implications of binding
the socket to a specific local port.
Return Value
A value of zero is returned if the connection was successful.
Otherwise, a non-zero error code is returned which indicates the
cause of the failure.
See Also
HostName Property,
KeepAlive Property,
NoDelay Property,
Options Property,
RemotePort Property,
ReuseAddress Property,
Route Property,
Secure Property,
SecureProtocol Property,
Timeout Property,
Bind Method,
Disconnect Method,
OnConnect Event,
OnDisconnect Event
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