Apple Newton Internet Enabler Spezifikationen PDF herunterladen (Seite 5)

Newton Technology Journal June 1996

if err then begin

print("link failed"); // handle the error

:endGrabLink(err); // end connect attempt

end

else // status.linkStatus = 'connected, so resolve name

DNSGetAddressFromName(“apple.com”, self, 'DNSCallback);

end;

The first statement, myLinkID:=linkID, saves the ID of the link

that InetGrabLink is in the process of grabbing in one of your

variables. You might want to store the link ID for use in other portions of

your application.

If grabbing of the link is progressing without errors, your callback

function gets called to report the progress. You can call the

InetDisplayStatus function, as shown in the above example. The

myStatView view used in the this example was created before the

grab of the link was initiated.

The grab of the link terminates when the connection is made or when an

error occurs. In either case, you can remove the status display view at that

point. To do so, call the InetDisplayStatus function with nil as

the value of the status parameter.

If InetGrabLink encounters an error, the error code will be a non-

zero value and your application has to do something with that error. In the

example function, a message is displayed and the connection attempt is

terminated.

If InetGrabLink succeeds, the callback receives 'connected

as the value of linkStatus. At that point, you can perform any

operations that are appropriate. The example function takes this

opportunity to convert its remote echo host name into an IP address, which

is saved in a local variable by the DNSCallback function.

Retrieving and Displaying Link Status Information

Many applications want to display status to the user while a net

connection is being established. Newton Internet Enabler makes this easy

for you with the InetDisplayStatus function, which displays link

status information on the Newton screen. Here is the declaration of the

function:

statusView InetDisplayStatus(linkID, statusView, status)

You can use the InetDisplayStatus function in three ways, as

follows:

• to create a new status view, pass nil as the value of each parameter:

myStatusView := InetDisplayStatus(nil, nil, nil);

• to display status for a link in an existing status view, pass in the link ID,

the status view, and the status frame that was sent to your callback

function:

InetDisplayStatus(myLinkID, myStatusView, myStatus);

• to remove and dispose of the status view, pass nil as the value of the

status frame:

InetDisplayStatus(myLinkID, myStatusView, nil);

The InetStatusDisplay function creates and uses a view that is

based on protoStatusTemplate. For information about this

proto, see the chapter “Additional System Services” in Newton

Programmer’s Guide.

To initiate the status display, you need to open the status view. The most

convenient place to do this is just before your call to the

InetGrabLink function. For example, the following function creates

the status view, stores it in myStatView for subsequent use, and then

calls the InetGrabLink function:

DoGrabLink := func()

begin

myStatView := InetDisplayStatus(nil, nil, nil);

InetGrabLink(nil, self, 'GrabLinkCallback);

end;

While the grab operation is in progress, you can update the status display

whenever your callback function gets called. For example, the following

code segment from a grab link callback function updates the status display if

no errors have occurred and if the link status has not yet become

'connected

if err = nil and status.linkStatus <> 'connected then

InetDisplayStatus(linkID, myStatView, stat);

When the grab operation is done, you can remove the status display.

The following code segment from a grab link callback function removes the

status display when the link status becomes '

connected

if err = nil and status.linkStatus = 'connected then

InetDisplayStatus(linkID, myStatView, nil);

The view displayed by the InetDisplayStatus function contains

a button that the user can tap to call the InetCancelLink function,

which cancels the grab operation that is currently in progress.

Configuring Newton Internet Enabler for Your Endpoint

After grabbing your Newton Internet Enabler link, you need to instantiate

your endpoint. You send the Instantiate message to your endpoint

with the options required to configure Newton Internet Enabler for your

application.

You must set three options in your Instantiate message:

• The 'inet service identifier option, which tells the Newton system

software to use Newton Internet Enabler with your endpoint.

• The Inet tool physical link ('ilid') option, which tells Newton Internet

Enabler which link ID to use for your endpoint. Use the link ID that was

returned by the InetGrabLink function.

• The Inet tool transport service type ('itsv' ) option, which tells Newton

Internet Enabler which transport type (for example, UDP or TCP) to use

for your endpoint.

Binding Your Endpoint with Newton Internet Enabler

After you instantiate your endpoint, you need to bind it to an address.

You either bind your endpoint to connect (initiate an outgoing connection),

or to listen for an incoming connection. If you are binding an endpoint that

is going to listen, you always need to pass the Inet local port ('ilpt') option

when you send the Bind message to your endpoint. If you are binding an

endpoint that is going to connect, you need to pass the Inet local port

option for UDP links, but not for TCP links.

The Inet local port option has two data slots that you specify: a short

value, InetPortNumber, and a Boolean value,

useDefaultPort. The useDefaultPort value only applies

when you are binding an endpoint to connect over a UDP link. Assign the

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