Apple Newton Internet Enabler Spezifikationen PDF herunterladen (Seite 7)

Newton Technology Journal June 1996

type: 'option,

opCode: opGetCurrent,

result: nil,

form: 'template,

data: {

arglist:

[

0, // host addr - byte 1

0, // host addr - byte 2

0, // host addr - byte 3

0, // host addr - byte 4

0, // host port number

typelist: kPortAddrStruct,

[

'struct,

'byte,

'short

]

}

inputScript: func(ep, data, terminator, options)

begin

// do something with data

end,

completionScript: func(ep, options, result)

begin

// skip error handling for canceled requests

if result <> kCommAbortErr then

begin

print("Error: " && result);

ep:DoDisconnect();

end;

end,

}

try

ep:SetInputSpec(streamInputSpec);

onexception |evt.ex.comm| do

return :DoDisconnect();

The example input specification frame above tells Newton Internet

Enabler to receive a packet of data from the UDP link and provides two

scripts: the inputScript function to process normal completion of data

reception and the completionScript function to process

unexpected termination of data reception. In addition, this input spec

includes a “get” of the UDP source socket address, which will be filled in

with the IP address of the host that sent the datagram to your application.

For TCP links, you do not need to include any options or specify any

receive flags in your input specification frame. For example, the following code

segment receives a carriage return-terminated string from a TCP connection.

local streamInputSpec := {

form: 'string,

termination: {endSequence: UnicodeCR},

discardAfter: 256,

inputScript: func(ep, data, terminator, options)

begin

// do something with data

end,

completionScript: func(ep, options, result)

begin

// skip error handling for canceled requests

if result <> kCommAbortErr then

begin

print("Error: " && result);

ep:DoDisconnect();

end;

end,

}

try

ep:SetInputSpec(streamInputSpec);

onexception |evt.ex.comm| do

return :DoDisconnect();

The example input specification frame above tells Newton Internet

Enabler to terminate input upon receiving a Unicode carriage return character

and provides two scripts: the inputScript function to process normal

completion of data reception and the completionScript function to

process unexpected termination of data reception.

You can also receive expedited data over a TCP link. When expedited

data arrives, your application is immediately notified: the link controller

sends an application event frame. The eventCode slot of this event

frame has the value kEventToolSpecific and the data slot is the

byte that was received.

See the chapter “Endpoint Interface” in Newton Programmer’s Guide for

detailed information about input specifications, the SetInputSpec

method, handling communications events, and other styles of receiving data

with an endpoint.

Disconnecting Your Endpoint

When you have finished using your endpoint, you need to disconnect,

unbind, and dispose of it. The following function shows you an example of

finishing your use of an endpoint.

MyApp.DoDisconnect := func()

begin

if ep then begin // ignore all disconnect errors

try

ep:Disconnect(true, nil);

onexception |evt.ex.comm| do

nil;

try

ep:UnBind(nil)

onexception |evt.ex.comm| do

nil;

try

ep:Dispose()

onexception |evt.ex.comm| do

nil;

end;

Releasing Your Link

After your application is completely done with the link, or whenever you will

not be using the link for a long period of time (approximately 15 minutes or

longer), you need to release it by calling the InetReleaseLink

function. If no other applications are using the link, the Newton system

software shuts it down.

You need to provide InetReleaseLink with a link ID, a callback

function, and a callback context frame:

InetReleaseLink(linkID, clientContext, clientCallback)

USING THE DOMAIN NAME SERVICE INTERFACE

You can use the Newton Internet Enabler domain name service functions to

translate between host name and Internet address representations. Newton

Internet Enabler provides the following domain name service global functions:

• the DNSCancelRequests function cancels any pending DNS

requests.

• the DNSGetAddressFromNamefunction translates a

domain name into its corresponding Internet address.

• the DNSGetMailAddress function translates a domain name

into the Internet address for a mail server that serves that domain.

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