Web Callback

Web Callback

Web callback – Wikipedia

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A typical Web callback form
Web callback is a technology where a person can enter his or her telephone number in a form on a web site. The company who owns that Web site will then receive the Web callback request and a call center agent will call the person who made the request back on the number they entered.
In some implementations, the Web callback service provider will place outgoing calls to the owner of the web site, and the user, then connect the calls together. An alternative approach is for the web site owner to receive a SMS text message, so they can initiate the call to the web site user.
Some Web callback service providers allow the callback form to be embedded into the web site, sometimes matching the look and feel of the existing site. Others simply add a hyperlink to the site, which is linked to the service providers own site.
Web Callback vs Click To Call[edit] Different than a simple computer Click To Call (CTC), Web Callbacks are not calls generated from the users computer, but will call any number entered.
Trends[edit] As more advanced Web Callback technology is becoming more available, businesses are finding it a useful tool to increase inbound marketing. Along with normal businesses that you would expect to use the tech, that want more calls from their website, the Pay Per Call Industry or Pay Per Call Arbitrage is now seeing an increase use of Web Callback technology to deliver more calls to their clients.
External links[edit] Definition of Web callback at
Web Service Callbacks - Oracle Help Center

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Web Service Callbacks – Oracle Help Center

Web services typically use HTTP to provide
communication between a client and a server (where the web service resides). HTTP
is a request-response protocol where each
operation consists of a request-response pair: (1) a request message sent from
the client to a server followed by (2) a response message returned from the server
to the client. The server must always send a response for the operation to complete
successfully. Such requests are called synchronous because during the
request the client is synchronized with the server; the client cannot continue
processing until the server responds or the request times out (the client may
time out if a response is not received within a specific period of time).
Some of the operations the web service performs may be long-running.
If an operation involves human interaction such as approval by a loan officer
of a bank, the operation could take days to complete. It would be a poor design
if individual request-response cycles were allowed to span days; such requests
would unnecessarily engage resources on both the client and server hosts.
With Workshop and WebLogic Server, you can design your web service
to be asynchronous, which means that the service disengages from the
client after the initial request and calls back the client when the final
response is ready. This allows the client to continue performing other work while
the application completes the requested operation. It also keeps each request-response
interaction between the client and application as short as possible. Think of
phoning a friend to request some information. If your friend doesn’t have the
answer right away, you wouldn’t sit on hold for hours at a time. Instead you would
ask the friend to call you back when he gets the information.
An asynchronous web service provides a method that accept requests from clients
that begin an operation but do not wait for the operation to complete.
The method typically returns immediately, supplying the response portion of
the initial request-response interaction but not supplying the actual,
substantial result of the requested operation. The service also provides a
callback method, which sends the results of the long-running operation to
the client when the results are finally ready.
The following diagram shows a web service with two methods: an initiating
method and a callback method. The client (typically a web service control)
invokes requestMessage to initiate the web service’s main process. When the
main process is complete (that is, when the response is constructed) the onMessage
callback method is invoked that sends the response back to the client.
Adding Callback Methods to a Web Service
To add a callback method to a web service, right-click anywhere in the web
service source code and select Insert > Callback. The
default callback interface containing one callback method will be added. By
default the callback method is named newMethod(). In the example below, the
default method name has been changed to sendMessage().
public class HelloWorldWebService {
private CallbackSvc callback;
public void requestMessage() {}
public interface CallbackSvc extends CallbackInterface {
public void onMessage();}}
Multiple callback methods can be added to the callback interface.
Parameters added to the callback method represent data sent to the client. For
example, if you want to send a String response back to the client, add a String
parameter to the callback method as follows.
public void sendMessage(String message);}
To send a response back to the client, you must (1) declare the callback
interface and then (2) invoke the appropriate callback method based on that
(1) To declare the callback interface, use the @Callback annotation. (The
Insert > Callback command will automatically supply this declaration. )
(2) Then invoke the appropriate callback method:
public class HelloMessage {
public void initiateRequest() {
ndMessage(“This is your callback message. “);}
public void sendMessage(String message);}}
Typically, a web service communicates with its client through a service control.
The diagram below shows the relationship between a web service client, a service
control, and a web service.
The client (on the far left) begins the interaction by requesting a message,
a request that is passed on to the web service through the web service control.
When the web service has completed the response, it is passed back to the original
client. This process has three stages: (1) The web service invokes its callback
method that sends the response to the control. (2) The control event set method
listens for the response and passes it to the client. (3) Finally the client handler
method listens for the control event set method and receives the event.
For more information about the relationship between a web service and a web
service control, see Handling
Web Service Callback Messages.
For more information about the relationship between a client and a web service
control, see Creating
and Using a Service Control.
For more information about testing Web Service callback methods see Testing
Web Service Callback Methods.
HTTP callbacks (webhooks): Connection Overrides - Twilio

HTTP callbacks (webhooks): Connection Overrides – Twilio

Twilio uses HTTP callbacks (webhooks) to let your application know when events happen, such as receiving an SMS message or getting an incoming phone call. When the event occurs, Twilio makes an HTTP request (usually a POST or a GET) to the URL you configured for the webhook. Twilio’s request will include details of the event such as the incoming phone number or the body of an incoming message.
Twilio’s use of HTTP URLs conforms to the standard syntax of a generic URI/URL.
Connection Overrides
Twilio has implemented URL extensions, that can be added to the standard HTTP webhook URL. These extensions give you the ability to override Twilio’s default HTTP callbacks connection settings on a per request basis. The override settings allow you to specify:
Longer timeouts to better support intermittent network issues between Twilio and your server/application
Shorter timeouts to speed up failover (to fallback URL) in the case of an outage on your server/application
HTTP callback connection retries on failures/timeouts
The egress Twilio Edge for your HTTP callback
The total timeout limit for all of the retries to complete
The use of Server Name Indication (SNI) if your server/application requires SNI to ensure a proper TLS handshake for all attempts
Connection overrides will be passed on a per webhook URL basis in the form of “fragments”. These fragments will contain key-value pairs; key and value are separated by =, pairs are separated by &. The 1st key-value pair start with #.
The complete list of overrides supported are detailed below:
Valid values
Connect Timeout (ct)
Min: 100
Max: 10000
The timeout in milliseconds Twilio will wait to establish its TCP connection to your webserver.
Read Timeout(rt)
Max: 15000
The amount of time in milliseconds after sending your webhook an HTTP request that Twilio will wait for the initial HTTP response packet. Also applies to the amount of time Twilio will wait between individual packets within your HTTP response.
Total time(tt)
The total time allowed for all timeouts including retries. If not set, the maximum limit is enforced.
Retry count(rc)
Min: 0
Max: 5
The number of retry attempts Twilio will make if its connection to your webhook fails.
To make sure you capture the behaviours you need, make sure to set the Retry Policy( rp) value below accordingly
Retry policy(rp)
4xx, 5xx, ct, rt, all
The type of failure to retry on:
4xx — Any 4xx response from your webserver
5xx — Any 5xx response from your webserver
ct — TCP connect or TLS handshake failure
rt — No response received within read timeout from your webserver. We will not retry on partial response, e. g., missing HTTP content.
all — All of the above.
Pass as a list of values, e. g., rp=ct, rt
SNI (sni)
y, n or unset
If set to y we use SNI for all webhooks to customer (including retry) set to n we disable SNI for all parameter not set the initial request will use SNI, but the retry will not.
Note Only applies for secure connections (HTTPS)
Edge Location(e)
ashburn, dublin, frankfurt, sao-paulo, singapore, sydney, tokyo, or umatillaashburn-ix, frankfurt-ix, london-ix, san-jose-ix, or singapore-ix (only used with Twilio Interconnect)
The Twilio edge location where webhooks egress. This can be a list and we rotate through the list as retries happen.
The order of precedence for edge location: (1) Twilio Interconnect Edge if specified in e=, (2) Static Proxy if enabled, (3) Public Edge if specified in e=, (4) DefaultIf staticproxy is enabled for the account, the e parameter is ignored.
There will be a new HTTP header (I-Twilio-Idempotency-Token), a unique string, that you can use to distinguish retry attempts.
Due to the real-time nature of voice calls, there is a hard upper timeout of 15 seconds imposed by Twilio on all call-related HTTP requests. This hard limit overrides any of the timers described above on call-processing requests, and is present to help to ensure a good end-user calling experience.
There are also other product and resource-related timers which may supercede these timers; please review your product documentation to help you determine appropriate settings for your use-case.
(1) Connection timeout (time to wait for a connection to be established) of one second.
(2) Connection timeout (time to wait for a connection to be established) of one second and a Read timeout (time to wait for data to be returned on a connection) of one second.
(3) Retry on both connect and read timeout, while also reducting the read timeout to five seconds.
(4) Retry on failure over different edge location. First attempt goes out over Ashburn, second attempt goes out over Umatilla (Oregon).
(5) Retry on connection failure, but with a one-second connection timeout. If there is no connection in one second, retry twice, i. e., for a total of three attempts to connect.
Where are these Overrides Available?
Connection overrides are available on all product webhooks except for Twilio Conversations. The overrides may be specified in webhook URLs in both the API resource properties and TwiML attributes.
If you have trouble implementing a connection override, you can reach out to our support team for help.
Need some help?
We all do sometimes; code is hard. Get help now from our support team, or lean on the wisdom of the crowd by visiting Twilio’s Community Forums or browsing the Twilio tag on Stack Overflow.

Frequently Asked Questions about web callback

What is a callback web service?

Web services typically use HTTP to provide communication between a client and a server (where the web service resides). It also keeps each request-response interaction between the client and application as short as possible. … Think of phoning a friend to request some information.

What is an HTTP callback?

Twilio uses HTTP callbacks (webhooks) to let your application know when events happen, such as receiving an SMS message or getting an incoming phone call. When the event occurs, Twilio makes an HTTP request (usually a POST or a GET ) to the URL you configured for the webhook.

What is web calling?

What is Web Calling? Phone.com Web Calling is the ability to make and receive calls using just your web browser, no need to install any apps! … It uses the internet and Phone.com servers to connect your call to any phone number in the world.

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