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Short Message Service (SMS) is a text messaging service used by
mobile communication devices to exchange brief text messages. Most
service providers also provide gateway servers that can be used to send
messages to a wireless device on their network using standard email
protocols. The Text Message control provides methods that can be used to
determine the provider associated with a specific telephone number and
send a text message to the device using the provider's mail gateway.
The first step your application must take is to initialize the
library, which will load the required system libraries and initialize
the internal data structures that are used. If the control is placed on
a form, then the container automatically handles the initialization of
control. If the control is created dynamically, then your application is
responsible for initialization.
Initialize
Initialize the control and load the Windows Sockets control for the
current process. If the control is created dynamically using a method
similar to CreateObject, then the application must call this
method to initialize the component before setting any properties or
calling any other methods in the control.
Uninitialize
Unload the Windows Sockets library and release any resources that
have been allocated for the current process. This is the last method
call that the application should make prior to terminating. This is
only necessary if the application has previously called the
Initialize method.
Text Messages
Sending a text message is done with a single method call with several
optional parameters. By default, messages are sent via an SMTP gateway,
however the control was designed to be extensible so that additional
methods could be integrated into future versions of the controls. For
example, a third-party company may offer a service that allows messages
to be sent using HTTP and that can be added as an additional service
type.
Message
This property is used to specify the current message text. In most
cases, a message should not exceed 160 characters in length, although
some service providers may accept longer messages. If a message
exceeds the maximum number of characters accepted by a service
provider, the message may be ignored or it may be split into multiple
messages.
PhoneNumber
This property is used to specify the current phone number for the
device you want to send a message to. This can be a standard E.164
formatted phone number or an unformatted number. Any extraneous
whitespace, punctuation or other non-numeric characters in the string
will be ignored.
Sender
This property is used to specify the email address of the sender when
the SMTP service is used to send the message. For other service types,
this property typically specifies the phone number or shortcode
associated with the sender.
Urgent
This property specifies whether a message will be flagged as urgent or
not. If this property is set to True, the message will sent with a
high priority. Note that this does not guarantee the message will be
received any differently than a standard text message. Each wireless
service provider may handle urgent messages differently, and some
providers may simply ignore the message priority.
SendMessage
This method is used to send a text message. It accepts one or more
optional parameters that can specify the sender, recipient and content
of the message, or if no parameters are specified, will use the
PhoneNumber, Sender and Message property values.
Relaying Messages
When a text message is sent using the SMTP service, the default
action is to attempt to connect directly to the wireless service
provider's gateway server. However, many residential Internet service
providers (ISPs) do not permit their customers to connect to third-party
mail servers and will block the outbound connection. Some wireless
service providers may also reject messages that originate from
residential IP addresses.
To resolve this issue, the developer should allow the user to specify
an alternate mail server that will relay the message to the wireless
service provider. For residential users, this will typically be the mail
server provided by their ISP. For business users, this will usually be
their corporate mail server. The ServerName and ServerPort
properties are used to identify the relay server, and the UserName
and Password properties provide the credentials to authenticate
the client session.
Relay
This property is used to determine if the control will send the
message directly to the wireless service provider's gateway server, or
if the message will be relayed through another mail server.
ServerName
This property is used to specify the host name or IP address of the
server that will relay the message.
ServerPort
This property is used to specify the port number that will be used to
establish the connection with the relay server. For SMTP servers, this
would typically either be port 25 or port 587.
UserName
This property is used in conjunction with the Password property
to authenticate the client session. If the message is being sent using
SMTP, this would typically be the user name or email address of the
person sending the message.
Password
This property is used in conjunction with the UserName property
to authenticate the client session. If the message is being sent using
SMTP, this would be the password associated with the user name.
Service Providers
When a service provider is mentioned in the documentation, typically
it is referring to the wireless service provider (also commonly called a
"carrier") that is responsible for providing network access for the
mobile device. These are identified by name, such as "Verizon Wireless"
and "AT&T Mobility". The control has a built-in table of known providers
in North America, and can return this information to your application.
Note that in some cases, a service provider may also refer to a specific
service used to send a text message.
Provider
This property the preferred wireless service provider associated with
the current phone number. Changing the value of this property will
change the preferred wireless service provider. If this property is an
empty string, the default provider assigned to the recipient's phone
number will be used.
ProviderCount
This property returns the number of wireless service providers
supported by the control. This property is used in conjunction with
the ProviderName property to enumerate all of the supported
service providers.
ProviderName
This property array returns the name of supported
wireless service provider and is used in conjunction with the
ProviderCount property to enumerate all of the supported
service providers. Typically this done to populate a user-interface
control that enables the user to select a preferred service provider.
GetAddress
This method can be used obtain the email address for the wireless
service provider's gateway that is associated with a phone number. This is done by sending an query to a
server that will check the phone number against a database of known
providers and the phone numbers that have been allocated for wireless
devices.
GetProvider
This method can be used to obtain the name of the service provider
associated with a phone number. This is done by sending an query to a
server that will check the phone number against a database of known
providers and the phone numbers that have been allocated for wireless
devices.
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