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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>
Direct Sockets API
</title>
<script src="https://www.w3.org/Tools/respec/respec-w3c" class="remove" defer></script>
<script class='remove'>
var respecConfig = {
specStatus: "unofficial",
github: {
repoURL: "WICG/direct-sockets",
branch: "main"
},
group: "wicg",
editors: [
{
name: "Andrew Rayskiy",
company: "Google Inc.",
companyURL: "https://google.com",
w3cid: 135463
}
],
formerEditors: [
{
name: "Eric Willigers",
company: "Google Inc.",
companyURL: "https://google.com",
w3cid: 67534
},
],
latestVersion: null,
xref: ["web-platform", "streams", "permissions-policy", "HTML", "infra", "DOM", "webidl", "isolated-contexts"],
// eventually add mdn: true, and caniuse: "direct-sockets"
};
</script>
</head>
<body data-cite="Direct Sockets">
<section id="abstract">
<p>
This specification defines an API that allows web applications to talk
to servers and devices that have their own protocols incompatible with
those available on the web.
</p>
</section>
<section id="sotd">
This is a work in progress. All <a
href="https://github.com/WICG/direct-sockets">contributions</a> welcome.
</section>
<section data-dfn-for="TCPSocket">
<h2>
{{TCPSocket}} interface
</h2>
<pre class="idl">
[
Exposed=(Window,DedicatedWorker),
SecureContext,
IsolatedContext
]
interface TCPSocket {
constructor(DOMString remoteAddress,
unsigned short remotePort,
optional TCPSocketOptions options = {});
readonly attribute Promise<TCPSocketOpenInfo> opened;
readonly attribute Promise<undefined> closed;
Promise<undefined> close();
};
</pre>
<p>
Methods on this interface typically complete asynchronously, queuing work on the
<dfn>TCPSocket task source</dfn>.
<p>
Instances of {{TCPSocket}} are created with the internal slots described in the following
table:
<table class="simple" data-dfn-for="TCPSocket">
<tr>
<th>Internal slot
<th>Initial value
<th>Description (non-normative)
<tr>
<td><dfn>[[\readable]]</dfn>
<td>`null`
<td>A {{ReadableStream}} that receives data from the socket
<tr>
<td><dfn>[[\writable]]</dfn>
<td>`null`
<td>A {{WritableStream}} that transmits data to the socket
<tr>
<td><dfn>[[\openedPromise]]</dfn>
<td>`new Promise`
<td>A {{Promise}} used to wait for the socket to be opened. Corresponds to the
{{TCPSocket/opened}} member.
<tr>
<td><dfn>[[\closedPromise]]
<td>`new Promise`
<td>A {{Promise}} used to wait for the socket to close or error. Corresponds to the
{{TCPSocket/closed}} member.
</table>
<section>
<h3><dfn>constructor()</dfn> method</h3>
<aside class="example">
In order to communicate via TCP a socket connection must be requested first. The socket
object constructor
allows the site to specify the necessary parameters which control how data is transmitted
and received.
<pre class="js">
const socket = new TCPSocket(/*remoteAddress=*/, /*remotePort=*/, /*options=*/);
</pre>
The developer should wait for the {{TCPSocket/opened}} promise to be resolved to gain access
to {{TCPSocketOpenInfo/readable}} and {{TCPSocketOpenInfo/writable}} streams.
<pre class="js">
const { readable, writable } = await socket.opened;
</pre>
Once {{TCPSocket/opened}} has resolved, the {{TCPSocketOpenInfo/readable}} and
{{TCPSocketOpenInfo/writable}}
can be accessed to get the {{ReadableStream}} and {{WritableStream}} instances for receiving
data from and sending data to the socket.
</aside>
The {{TCPSocket/constructor()}} steps are:
<ol>
<li>
If [=this=]'s [=relevant global object=]'s [=associated Document=] is
not [=allowed to use=] the [=policy-controlled feature=] named "[=policy-controlled
feature/direct-sockets=]", throw a
"{{NotAllowedError}}" {{DOMException}}.
<li>
If |options|["{{TCPSocketOptions/keepAliveDelay}}"] is less than 1,000, throw a
{{TypeError}}.
<li>
If |options|["{{TCPSocketOptions/sendBufferSize}}"] is equal to 0, throw a {{TypeError}}.
<li>
If |options|["{{TCPSocketOptions/receiveBufferSize}}"] is equal to 0, throw a
{{TypeError}}.
<li>
Perform the following steps [=in parallel=].
<ol>
<li>
Invoke the operating system to open a TCP socket using the given |remoteAddress| and
|remotePort| and the connection parameters (or their defaults) specified in |options|.
<li>
If this fails for any reason, [=queue a global task=] on the [=relevant global
object=] of
[=this=] using the [=TCPSocket task source=] to run the
following steps:
<ol>
<li>
[=Reject=] the {{TCPSocket/[[openedPromise]]}} with a "{{NetworkError}}"
{{DOMException}}.
<li>
[=Reject=] the {{TCPSocket/[[closedPromise]]}} with a "{{NetworkError}}"
{{DOMException}}.
</ol>
<li>
On success, [=queue a global task=] on the [=relevant global object=] of
[=this=] using the [=TCPSocket task source=] to run the
following steps:
<ol>
<li>
[=initialize TCPSocket readable stream|Initialize=] {{TCPSocket/[[readable]]}}.
<li>
[=initialize TCPSocket writable stream|Initialize=] {{TCPSocket/[[writable]]}}.
<li>
Let |openInfo:TCPSocketOpenInfo| be a new {{TCPSocketOpenInfo}}.
<li>
Set |openInfo|["{{TCPSocketOpenInfo/readable}}"] to
[=this=].{{TCPSocket/[[readable]]}}.
<li>
Set |openInfo|["{{TCPSocketOpenInfo/writable}}"] to
[=this=].{{TCPSocket/[[writable]]}}.
<li>
Populate the remaining fields of |openInfo| using the information provided by the
operating system:
|openInfo|["{{TCPSocketOpenInfo/remoteAddress}}"],
|openInfo|["{{TCPSocketOpenInfo/remotePort}}"],
|openInfo|["{{TCPSocketOpenInfo/localAddress}}"] and
|openInfo|["{{TCPSocketOpenInfo/localPort}}"].
<li>
[=Resolve=] [=this=].{{TCPSocket/[[openedPromise]]}} with |openInfo|.
</ol>
</ol>
</ol>
<section data-dfn-for="TCPSocketOptions">
<h4><dfn>TCPSocketOptions</dfn> dictionary</h4>
<pre class="idl">
enum SocketDnsQueryType {
"ipv4",
"ipv6"
};
dictionary TCPSocketOptions {
[EnforceRange] unsigned long sendBufferSize;
[EnforceRange] unsigned long receiveBufferSize;
boolean noDelay = false;
[EnforceRange] unsigned long keepAliveDelay;
SocketDnsQueryType dnsQueryType;
};
</pre>
<dl>
<dt>
<dfn>sendBufferSize</dfn> member
</dt>
<dd>
The requested send buffer size, in bytes.
If not specified, then platform-specific default value will be used.
</dd>
<dt>
<dfn>receiveBufferSize</dfn> member
</dt>
<dd>
The requested receive buffer size, in bytes.
If not specified, then platform-specific default value will be used.
</dd>
<dt>
<dfn>noDelay</dfn> member
</dt>
<dd>
Enables the `TCP_NODELAY` option,
disabling <a href="https://en.wikipedia.org/wiki/Nagle%27s_algorithm">Nagle's
algorithm</a>.
<div class="note">
No-Delay is disabled by default.
</div>
</dd>
<dt>
<dfn>keepAliveDelay</dfn> member
</dt>
<dd>
If specified, enables TCP Keep-Alive by setting `SO_KEEPALIVE` option on the socket
to `true`. The way the actual delay is set is platform-specific:
<ol>
<li>
On Linux & ChromeOS `keepAliveDelay` is applied to `TCP_KEEPIDLE` and
`TCP_KEEPINTVL`;
<li>
On MacOS `keepAliveDelay` affects `TCP_KEEPALIVE`;
<li>
On Windows `keepAliveDelay` is replicated to `keepalivetime` and `keepaliveinterval`
of <a href="https://learn.microsoft.com/en-us/windows/win32/winsock/sio-keepalive-vals">`SIO_KEEPALIVE_VALS`</a>.
</ol>
<div class="note">
Keep-Alive is disabled by default.
</div>
</dd>
<dt>
<dfn>dnsQueryType</dfn> member
</dt>
<dd>
Indicates whether IPv4 or IPv6 record should be returned during DNS lookup.
If omitted, the OS will select the record type(s) to be queried automatically
depending on IPv4/IPv6 settings and reachability.
</dd>
</dl>
</section>
</section>
<section>
<h3>{{TCPSocket/[[readable]]}} attribute (internal)</h3>
<aside class="example">
An application receiving data from a TCP socket will typically use the {{ReadableStream}}
like this:
<pre class="js">
const { readable } = await socket.opened;
const reader = readable.getReader();
while (true) {
const { value, done } = await reader.read();
if (done) {
// |reader| has been canceled.
break;
}
// Do something with |value|...
}
reader.releaseLock();
</pre>
</aside>
The steps to <dfn data-lt="initialize TCPSocket readable stream">initialize the TCPSocket
readable stream</dfn> are:
<ol>
<li>
Let |stream:ReadableStream| be a [=new=] {{ReadableStream}}.
<li>
Let |pullAlgorithm| be the following steps:
<ol>
<li>
Let |desiredSize| be the
[=ReadableStream/desired size to fill up to the high water mark=] for
[=this=].{{TCPSocket/[[readable]]}}.
<li>
If [=this=].{{TCPSocket/[[readable]]}}'s [=ReadableStream/current BYOB request view=]
is non-null, then set |desiredSize| to [=this=].{{TCPSocket/[[readable]]}}'s
[=ReadableStream/current BYOB request view=]'s [=BufferSource/byte length=].
<li>
Run the following steps in parallel:
<ol>
<li>
Invoke the operating system to read up to |desiredSize| bytes from the socket,
placing the result in the [=byte sequence=] |bytes|.
<li>
[=Queue a global task=] on the [=relevant global object=] of
[=this=] using the [=TCPSocket task source=] to run the
following steps:
<ol>
<li>
If the connection was closed gracefully, run the following steps:
<ol>
<li>
Invoke [=ReadableStream/close=] on [=this=].{{TCPSocket/[[readable]]}}.
<li>
Invoke the steps to [=handle closing the TCPSocket readable stream=].
</ol>
<div class="note">
This is triggered by the peer sending a packet with the FIN flag set
and is typically indicated by the operating system returning 0 bytes
when asked for more data from the socket.
</div>
<li>
If no errors were encountered, then:
<ol>
<li>
If [=this=].{{TCPSocket/[[readable]]}}'s
[=ReadableStream/current BYOB request view=] is non-null,
then [=ArrayBufferView/write=] |bytes| into
[=this=].{{TCPSocket/[[readable]]}}'s
[=ReadableStream/current BYOB request view=], and set
|view| to [=this=].{{TCPSocket/[[readable]]}}'s
[=ReadableStream/current BYOB request view=].
<li>
Otherwise, set |view| to the result of
[=ArrayBufferView/create|creating=] a {{Uint8Array}} from
|bytes| in [=this=]'s [=relevant Realm=].
<li>
[=ReadableStream/Enqueue=] |view| into
[=this=].{{TCPSocket/[[readable]]}}.
</ol>
<li>
If a network or operating system error was encountered, invoke
[=ReadableStream/error=] on [=this=].{{TCPSocket/[[readable]]}} with
a "{{NetworkError}}" {{DOMException}} and invoke the steps
to [=handle closing the TCPSocket readable stream=].
</ol>
</ol>
<li>
Return [=a promise resolved with=] `undefined`.
</ol>
<li>
Let |cancelAlgorithm| be the following steps:
<ol>
<li>
Invoke the steps to [=handle closing the TCPSocket readable stream=].
<li>
Return [=a promise resolved with=] `undefined`.
</ol>
<li>
[=ReadableStream/Set up with byte reading support=] |stream| with
<i>[=ReadableStream/set up with byte reading support/pullAlgorithm=]</i>
set to |pullAlgorithm|,
<i>[=ReadableStream/set up with byte reading support/cancelAlgorithm=]</i>
set to |cancelAlgorithm|, and
<i>[=ReadableStream/set up with byte reading support/highWaterMark=]</i>
set to an implementation-defined value.
<li>Set [=this=].{{TCPSocket/[[readable]]}} to |stream|.
</ol>
To <dfn>handle closing the TCPSocket readable stream</dfn> perform the following steps:
<ol>
<li>
If [=this=].{{TCPSocket/[[writable]]}} is active, abort these steps.
<li>
Run the following steps [=in parallel=].
<ol>
<li>
Invoke the operating system to close the socket.
<li>
[=Queue a global task=] on the [=relevant global object=] of
[=this=] using the [=TCPSocket task source=] to run the
following steps:
<ul>
<li>
If [=this=].{{TCPSocket/[[writable]]}} is errored,
[=reject=] [=this=].{{TCPSocket/[[closedPromise]]}}
with [=this=].{{TCPSocket/[[writable]]}}.`[[storedPromise]]`.
<li>
Otherwise, if [=this=].{{TCPSocket/[[readable]]}} is errored,
[=reject=] [=this=].{{TCPSocket/[[closedPromise]]}}
with [=this=].{{TCPSocket/[[readable]]}}.`[[storedPromise]]`.
<li>
Otherwise, [=resolve=] [=this=].{{TCPSocket/[[closedPromise]]}} with `undefined`.
</ul>
</ol>
</ol>
</section>
<section>
<h3>{{TCPSocket/[[writable]]}} attribute (internal)</h3>
<aside class="example">
To write individual chunks of data to the socket a
{{WritableStreamDefaultWriter}} can be created and released as necessary.
This example uses a `TextEncoder` to encode a {{DOMString}} as the
necessary {{Uint8Array}} for transmission.
<pre class="js">
const encoder = new TextEncoder();
const { writable } = await socket.opened;
const writer = writable.getWriter();
await writer.write(encoder.encode("PING"));
writer.releaseLock();
</pre>
The {{WritableStreamDefaultWriter/write()}} method returns a {{Promise}} which
resolves when data has been written. While having some data available in
the transmit buffer is important to maintain good throughput awaiting this
{{Promise}} before generating too many chunks of data is a good practice
to avoid excessive buffering.
</aside>
The steps to <dfn data-lt="initialize TCPSocket writable stream">initialize the TCPSocket
writable stream</dfn> are:
<ol>
<li>
Let |stream:WritableStream| be a [=new=] {{WritableStream}}.
<li>
Let |signal:AbortSignal| be |stream|'s [=WritableStream/signal=].
<li>
Let |writeAlgorithm| be the following steps, given |chunk|:
<ol>
<li>
Let |promise:Promise| be [=a new promise=].
<li>
Assert: |signal| is not [=AbortSignal/aborted=].
<li>
If |chunk| cannot be [=converted to an IDL value=] of type
{{BufferSource}}, reject |promise| with a {{TypeError}} and return
|promise|. Otherwise, save the result of the conversion in
|source:BufferSource|.
<li>
[=Get a copy of the buffer source=] |source| and save the result in
|bytes|.
<li>
[=In parallel=], run the following steps:
<ol>
<li>
Invoke the operating system to write |bytes| to the socket.
<div class="note">
The operating system may return from this operation once
|bytes| has been queued for transmission rather than after it
has been transmitted.
</div>
<li>
[=Queue a global task=] on the [=relevant global object=] of
[=this=] using the [=TCPSocket task source=] to run the
following steps:
<ol>
<li>
If the chunk was successfully written, [=resolve=] |promise| with `undefined`.
<div class="note">
[[STREAMS]] specifies that |writeAlgorithm| will only be
invoked after the {{Promise}} returned by a previous
invocation of this algorithm has resolved. For efficiency
an implementation is allowed to resolve this {{Promise}}
early in order to coalesce multiple chunks waiting in the
{{WritableStream}}'s internal queue into a single request
to the operating system.
</div>
<li>
If a network or operating system error was encountered:
<ol>
<li>
[=Reject=] |promise| with a "{{NetworkError}}"
{{DOMException}}.
<li>
Invoke the steps to [=handle closing the TCPSocket writable
stream=].
</ol>
<li>
If |signal| is [=AbortSignal/aborted=], [=reject=] |promise|
with |signal|'s [=AbortSignal/abort reason=].
</ol>
</ol>
<li>
Return |promise|.
</ol>
<li>
Let |abortAlgorithm| be the following steps:
<ol>
<li>
Let |promise| be [=a new promise=].
<li>
Run the following steps [=in parallel=]:
<ol>
<li>
Invoke the operating system to shutdown the socket for writing.
<li>
[=Queue a global task=] on the [=relevant global object=] of
[=this=] using the [=TCPSocket task source=] to run the
following steps:
<ol>
<li>
Invoke the steps to [=handle closing the TCPSocket writable stream=].
<li>
[=Resolve=] |promise| with `undefined`.
</ol>
</ol>
<li>
Return |promise|.
</ol>
<li>
Let |closeAlgorithm| be the following steps:
<ol>
<li>
Let |promise| be [=a new promise=].
<li>
Run the following steps [=in parallel=].
<ol>
<li>
Invoke the operating system to shutdown the socket for writing.
<li>
[=Queue a global task=] on the [=relevant global object=] of
[=this=] using the [=TCPSocket task source=] to run the
following steps:
<ol>
<li>
Invoke the steps to [=handle closing the TCPSocket writable stream=].
<li>
If |signal| is [=AbortSignal/aborted=], [=reject=] |promise|
with |signal|'s [=AbortSignal/abort reason=].
<li>
[=Resolve=] |promise| with `undefined`.
</ol>
</ol>
<li>
Return |promise|.
</ol>
<li>
[=WritableStream/Set up=] |stream| with
<i>[=WritableStream/set up/writeAlgorithm=]</i>
set to |writeAlgorithm|,
<i>[=WritableStream/set up/abortAlgorithm=]</i>
set to |abortAlgorithm|,
<i>[=WritableStream/set up/closeAlgorithm=]</i>
set to |closeAlgorithm|,
<i>[=WritableStream/set up/highWaterMark=]</i>
set to an implementation-defined value.
<li>
[=AbortSignal/Add=] the following abort steps to |signal|:
<ol>
<li>
Cause any invocation of the operating system to write to the
socket to return as soon as possible no matter how much data has
been written.
</ol>
<li>Set [=this=].{{TCPSocket/[[writable]]}} to |stream|.
</ol>
To <dfn>handle closing the TCPSocket writable stream</dfn> perform the following steps:
<ol>
<li>
If [=this=].{{TCPSocket/[[readable]]}} is active, abort these steps.
<li>
Run the following steps [=in parallel=].
<ol>
<li>
Invoke the operating system to close the socket.
<li>
[=Queue a global task=] on the [=relevant global object=] of
[=this=] using the [=TCPSocket task source=] to run the
following steps:
<ul>
<li>
If [=this=].{{TCPSocket/[[readable]]}} is errored,
[=reject=] [=this=].{{TCPSocket/[[closedPromise]]}}
with [=this=].{{TCPSocket/[[readable]]}}.`[[storedPromise]]`.
<li>
Otherwise, if [=this=].{{TCPSocket/[[writable]]}} is errored,
[=reject=] [=this=].{{TCPSocket/[[closedPromise]]}}
with [=this=].{{TCPSocket/[[writable]]}}.`[[storedPromise]]`.
<li>
Otherwise, [=resolve=] [=this=].{{TCPSocket/[[closedPromise]]}} with `undefined`.
</ul>
</ol>
</ol>
</section>
<section>
<h3><dfn>opened</dfn> attribute</h3>
<aside class="example">
The {{TCPSocket/opened}} is an attribute containing all information about the socket.
Once it is resolved, the developer can use the {{TCPSocketOpenInfo/readable}} and
{{TCPSocketOpenInfo/writable}}
to read from and write to the socket.
<pre class="js">
const { readable, writable } = await socket.opened;
const reader = readable.getReader();
// Read from the socket using |reader|...
const writer = writable.getWriter();
// Write to the socket using |writer|...
</pre>
</aside>
When called, returns the [=this=].{{TCPSocket/[[openedPromise]]}}.
<section data-dfn-for="TCPSocketOpenInfo">
<h4><dfn>TCPSocketOpenInfo</dfn> dictionary</h4>
<pre class="idl">
dictionary TCPSocketOpenInfo {
ReadableStream readable;
WritableStream writable;
DOMString remoteAddress;
unsigned short remotePort;
DOMString localAddress;
unsigned short localPort;
};
</pre>
<dl>
<dt>
<dfn>readable</dfn> member
</dt>
<dd>
The readable side of the socket. Set to {{TCPSocket/[[readable]]}}.
</dd>
<dt>
<dfn>writable</dfn> member
</dt>
<dd>
The writable side of the socket. Set to {{TCPSocket/[[writable]]}}.
</dd>
<dt>
<dfn>remoteAddress</dfn> member
</dt>
<dd>
Resolved remote IP address that the socket is connected to.
</dd>
<dt>
<dfn>remotePort</dfn> member
</dt>
<dd>
Remote port that the socket is connected to.
</dd>
<dt>
<dfn>localAddress</dfn> member
</dt>
<dd>
Local IP address that the socket is bound to.
</dd>
<dt>
<dfn>localPort</dfn> member
</dt>
<dd>
Local port that the socket is bound to.
</dd>
</dl>
</section>
</section>
<section>
<h3><dfn>closed</dfn> attribute</h3>
<aside class="example">
The {{TCPSocket/closed}} is an attribute that keeps track of the socket state.
It gets resolved if the socket is closed gracefully (i.e. by the user) or rejected in case
of an error.
<pre class="js">
socket.closed.then(() => console.log("Closed"), () => console.log("Errored"));
</pre>
Note that {{TCPSocket/closed}} will be automatically rejected or resolved once both
{{TCPSocket/[[readable]]}} and {{TCPSocket/[[writable]]}} reach a closed or errored state.
</aside>
When called, returns the [=this=].{{TCPSocket/[[closedPromise]]}}.
</section>
<section>
<h3><dfn>close()</dfn> method</h3>
<aside class="example">
When communication with the port is no longer required it can be closed
and the associated resources released by the system.
<p>
Calling `socket.`{{TCPSocket/close()}} implicitly invokes
`opened.`{{TCPSocketOpenInfo/readable}}`.`{{ReadableStream/cancel()}} and
`opened.`{{TCPSocketOpenInfo/writable}}`.`{{WritableStream/abort()}} in order to
clear any buffered data. If the application has called
`opened.`{{TCPSocketOpenInfo/readable}}`.`{{ReadableStream/getReader()}} or
`opened.`{{TCPSocketOpenInfo/writable}}`.`{{WritableStream/getWriter()}} the stream
is locked and the socket cannot be closed. This forces the developer to
decide how to handle any read or write operations that are in progress.
For example, to ensure that all buffered data has been transmitted before
the socket is closed the application must await the {{Promise}} returned by
`writer.`{{WritableStreamDefaultWriter/close()}}.
<pre class="js">
const encoder = new TextEncoder();
const { writable } = await socket.opened;
const writer = writable.getWriter();
writer.write(encoder.encode("A long message that will take..."));
await writer.close();
await socket.close();
</pre>
To discard any unsent data the application could instead call
`writer.`{{WritableStreamDefaultWriter/abort()}}.
If a loop is being used to read data from the socket, then it must be exited before calling
`socket`.{{TCPSocket/close()}}.
<pre class="js">
const { readable } = await socket.opened;
const reader = readable.getReader();
async function readUntilClosed() {
while (true) {
const { value, done } = await reader.read();
if (done) {
// |reader| has been canceled.
break;
}
// Do something with |value|...
}
await socket.close();
}
const read_complete = readUntilClosed();
// Sometime later...
reader.releaseLock();
await read_complete;
</pre>
</aside>
The {{TCPSocket/close()}} method steps are:
<ol>
<li>
If [=this=].{{TCPSocket/[[openedPromise]]}} is rejected or not yet resolved, [=reject=]
with
"{{InvalidStateError}}" {{DOMException}}.
<li>
If [=this=].{{TCPSocket/[[closedPromise]]}} is settled, return
[=this=].{{TCPSocket/[[closedPromise]]}}.
<li>
If [=this=].{{TCPSocket/[[readable]]}} or [=this=].{{TCPSocket/[[writable]]}} are <a
href="https://streams.spec.whatwg.org/#lock">locked</a>,
[=reject=] with "{{InvalidStateError}}" {{DOMException}}.
<li>
Let |cancelPromise:Promise| be the result of invoking
[=ReadableStream/cancel=] on [=this=].{{TCPSocket/[[readable]]}}.
<li>
Set |cancelPromise|.[[\PromiseIsHandled]] to true.
<li>
Let |abortPromise:Promise| be the result of invoking
[=WritableStream/abort=] on [=this=].{{TCPSocket/[[writable]]}}.
<li>
Set |abortPromise|.[[\PromiseIsHandled]] to true.
<li>
Return [=this=].{{TCPSocket/[[closedPromise]]}}.
</ol>
</section>
</section>
<section data-dfn-for="UDPSocket">
<h2>
{{UDPSocket}} interface
</h2>
<pre class="idl">
[
Exposed=(Window,DedicatedWorker),
SecureContext,
IsolatedContext
]
interface UDPSocket {
constructor(optional UDPSocketOptions options = {});
readonly attribute Promise<UDPSocketOpenInfo> opened;
readonly attribute Promise<undefined> closed;
Promise<undefined> close();
};
</pre>
Methods on this interface typically complete asynchronously, queuing work on the
<dfn>UDPSocket task source</dfn>.
<p>
Instances of {{UDPSocket}} are created with the internal slots described in the following
table:
<table class="simple" data-dfn-for="UDPSocket">
<tr>
<th>Internal slot
<th>Initial value
<th>Description (non-normative)
<tr>
<td><dfn>[[\readable]]</dfn>
<td>`null`
<td>A {{ReadableStream}} that receives data from the socket
<tr>
<td><dfn>[[\writable]]</dfn>
<td>`null`
<td>A {{WritableStream}} that transmits data to the socket
<tr>
<td><dfn>[[\openedPromise]]</dfn>
<td>`new Promise`
<td>A {{Promise}} used to wait for the socket to be opened. Corresponds to the
{{UDPSocket/opened}} member.
<tr>
<td><dfn>[[\closedPromise]]
<td>`new Promise`
<td>A {{Promise}} used to wait for the socket to close or error. Corresponds to the
{{UDPSocket/closed}} member.
</table>
<section>
<h3><dfn>constructor()</dfn> method</h3>
<aside class="example">
In order to communicate via UDP a socket must be opened first. The socket object constructor
allows the site to specify the necessary parameters which control how data is transmitted
and received.
<pre class="js">
const socket = new UDPSocket(/*options=*/);
</pre>
The developer should wait for the {{UDPSocket/opened}} promise to be resolved to gain access
to {{UDPSocketOpenInfo/readable}} and {{UDPSocketOpenInfo/writable}} streams.
<pre class="js">
const { readable, writable } = await socket.opened;
</pre>
Once {{UDPSocket/opened}} has resolved, the {{UDPSocketOpenInfo/readable}} and
{{UDPSocketOpenInfo/writable}}
can be accessed to get the {{ReadableStream}} and {{WritableStream}} instances for receiving
data from and sending data to the socket.
</aside>
{{UDPSocket}} can operate in either {{UDPSocket/connected}} or {{UDPSocket/bound}} <dfn>mode</dfn> which
is decided based on the provided set of constructor options.
<ul>
<li>
In <dfn>connected</dfn> {{UDPSocket/mode}}, the UDP socket is associated with a specific destination
IP address and port number. This means that any data sent using the socket is automatically
sent to the specified destination without the need to specify the address and port every
time. This {{UDPSocket/mode}} is assumed when {{UDPSocketOptions/remoteAddress}} and
{{UDPSocketOptions/remotePort}} are specified in {{UDPSocketOptions}}.
<div class="note">
This {{UDPSocket/mode}} is useful for applications that require a constant communication channel
between two endpoints, such as real-time streaming applications.
</div>
<li>
In <dfn>bound</dfn> {{UDPSocket/mode}}, the UDP socket is bound to a specific local IP address and port
number. This means that any data received on that IP address and port is delivered to the
socket. Similarly, any data sent using the socket is sent from the bound IP address and
port. This {{UDPSocket/mode}} is assumed when {{UDPSocketOptions/localAddress}} is specified in
{{UDPSocketOptions}}.
<div class="note">
This {{UDPSocket/mode}} is useful for applications that need to listen for incoming data on a
specific port or interface, such as server applications that receive incoming messages
from multiple clients.
</div>
</ul>
The {{UDPSocket/constructor()}} steps are:
<ol>
<li>
If [=this=]'s [=relevant global object=]'s [=associated Document=] is
not [=allowed to use=] the [=policy-controlled feature=] named "[=policy-controlled
feature/direct-sockets=]", throw a
"{{NotAllowedError}}" {{DOMException}}.
<li>
If only one of |options|["{{UDPSocketOptions/remoteAddress}}"] and
|options|["{{UDPSocketOptions/remotePort}}"] is specified, throw a {{TypeError}}.
<li>
Alternatively, if both |options|["{{UDPSocketOptions/remoteAddress}}"] and
|options|["{{UDPSocketOptions/remotePort}}"] are specified, assume {{UDPSocket/connected}}
{{UDPSocket/mode}}.
<li>
If |options|["{{UDPSocketOptions/localPort}}"] is equal to 0 or specified without
|options|["{{UDPSocketOptions/localAddress}}"], throw a {{TypeError}}.
<li>
If |options|["{{UDPSocketOptions/localAddress}}"] is specified:
<ol>
<li>
If {{UDPSocket/connected}} {{UDPSocket/mode}} was previously inferred, throw a {{TypeError}}.
<li>
If |options|["{{UDPSocketOptions/localAddress}}"] is not a valid IP address,
throw a {{TypeError}}.
<li>
Assume {{UDPSocket/bound}} {{UDPSocket/mode}}.
</ol>
<li>
If no {{UDPSocket/mode}} has been inferred at this point, throw a {{TypeError}}.
<li>
If |options|["{{UDPSocketOptions/dnsQueryType}}"] is specified in {{UDPSocket/bound}}
{{UDPSocket/mode}}, throw a {{TypeError}}.
<li>
If |options|["{{UDPSocketOptions/ipv6Only}}"] is specified:
<ol>
<li>
If inferred {{UDPSocket/mode}} is {{UDPSocket/connected}}, throw a {{TypeError}}.
<li>
If |options|["{{UDPSocketOptions/localAddress}}"] is not equal to the IPv6
unspecified address (`::`), throw a {{TypeError}}.
</ol>
<li>
If |options|["{{UDPSocketOptions/sendBufferSize}}"] is equal to 0, throw a {{TypeError}}.
<li>
If |options|["{{UDPSocketOptions/receiveBufferSize}}"] is equal to 0, throw a
{{TypeError}}.
<li>
Perform the following steps [=in parallel=].
<ol>
<li>
Invoke the operating system to open a UDP socket using the inferred
{{UDPSocket/mode}} and the parameters (or their defaults) specified in |options|.
<li>
If this fails for any reason, [=queue a global task=] on the [=relevant global
object=] of [=this=] using the [=UDPSocket task source=] to run the following steps:
<ol>
<li>
[=Reject=] the {{UDPSocket/[[openedPromise]]}} with a "{{NetworkError}}"
{{DOMException}}.
<li>
[=Reject=] the {{UDPSocket/[[closedPromise]]}} with a "{{NetworkError}}"
{{DOMException}}.
</ol>
<li>
On success, [=queue a global task=] on the [=relevant global object=] of
[=this=] using the [=UDPSocket task source=] to run the following steps:
<ol>
<li>
[=initialize UDPSocket readable stream|Initialize=] {{UDPSocket/[[readable]]}}.
<li>
[=initialize UDPSocket writable stream|Initialize=] {{UDPSocket/[[writable]]}}.
<li>
Let |openInfo:UDPSocketOpenInfo| be a new {{UDPSocketOpenInfo}}.