From 87a857865a83c63412bb465a9a570a63f10af8f1 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Lo=C3=AFc=20Hoguin?= Date: Wed, 8 Aug 2018 12:55:18 +0200 Subject: Gun 1.1 --- docs/en/gun/1.1/guide/websocket/index.html | 238 +++++++++++++++++++++++++++++ 1 file changed, 238 insertions(+) create mode 100644 docs/en/gun/1.1/guide/websocket/index.html (limited to 'docs/en/gun/1.1/guide/websocket/index.html') diff --git a/docs/en/gun/1.1/guide/websocket/index.html b/docs/en/gun/1.1/guide/websocket/index.html new file mode 100644 index 00000000..6b23e725 --- /dev/null +++ b/docs/en/gun/1.1/guide/websocket/index.html @@ -0,0 +1,238 @@ + + + + + + + + + + Nine Nines: Websocket + + + + + + + + + + + + + + +
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99s

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Websocket

+ +

This chapter describes how to use the Gun client for communicating with a Websocket server.

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HTTP upgrade

+

Websocket is a protocol built on top of HTTP. To use Websocket, you must first request for the connection to be upgraded. Only HTTP/1.1 connections can be upgraded to Websocket, so you might need to restrict the protocol to HTTP/1.1 if you are planning to use Websocket over TLS.

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You must use the gun:ws_upgrade/2,3,4 function to upgrade to Websocket. This function can be called anytime after connection, so you can send HTTP requests before upgrading to Websocket.

+
Upgrade to Websocket
+
+
gun:ws_upgrade(ConnPid, "/websocket").
+
+

Gun will set all the necessary headers for performing the Websocket upgrade, but you can specify additional headers if needed. For example you can request a custom sub-protocol.

+
Upgrade to Websocket and request a protocol
+
+
gun:ws_upgrade(ConnPid, "/websocket", [
+    {<<"sec-websocket-protocol">>, "mychat"}
+]).
+
+

You can pass the Websocket options as part of the gun:open/2,3 call when opening the connection, or using the gun:ws_upgrade/4. The fourth argument is those same options.

+

When the upgrade succeeds, a gun_upgrade message is sent. If the server does not understand Websocket or refused the upgrade, a gun_response message is sent. If Gun couldn't perform the upgrade due to an error (for example attempting to upgrade to Websocket on an HTTP/1.0 connection) then a gun_error message is sent.

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When the server does not understand Websocket, it may send a meaningful response which should be processed. In the following example we however ignore it:

+
+
receive
+    {gun_upgrade, ConnPid, StreamRef, [<<"websocket">>], Headers} ->
+        upgrade_success(ConnPid, StreamRef);
+    {gun_response, ConnPid, _, _, Status, Headers} ->
+        exit({ws_upgrade_failed, Status, Headers});
+    {gun_error, ConnPid, StreamRef, Reason} ->
+        exit({ws_upgrade_failed, Reason})
+    %% More clauses here as needed.
+after 1000 ->
+    exit(timeout)
+end.
+
+

Sending data

+

Once the Websocket upgrade has completed successfully, you no longer have access to functions for performing requests. You can only send and receive Websocket messages.

+

Use gun:ws_send/2 to send messages to the server.

+
Send a text frame
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+
gun:ws_send(ConnPid, {text, "Hello!"}).
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Note that if you send a close frame, Gun will close the connection cleanly but will attempt to reconnect afterwards.

+

Receiving data

+

Gun sends an Erlang message to the owner process for every Websocket message it receives.

+
+
receive
+    {gun_ws, ConnPid, StreamRef, Frame} ->
+        handle_frame(ConnPid, StreamRef, Frame)
+end.
+
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