From 396c8250295fe698d236cce195ba51e582ca2ad7 Mon Sep 17 00:00:00 2001
From: Roman Turchin <roman@turch.in>
Date: Thu, 12 Jun 2025 18:06:05 +0200
Subject: [PATCH 1/2] Allow to set custom websocket factory

---
 site/source/docs/porting/networking.rst |  3 +++
 src/lib/libsockfs.js                    | 13 +++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/site/source/docs/porting/networking.rst b/site/source/docs/porting/networking.rst
index 150661b8e778f..b8916989d5715 100644
--- a/site/source/docs/porting/networking.rst
+++ b/site/source/docs/porting/networking.rst
@@ -51,6 +51,9 @@ This is the default build mode for Emscripten. Use the linker flag
 to connect to, and the linker flag ``-sWEBSOCKET_SUBPROTOCOL`` or
 ``Module['websocket']['subprotocol']`` to control the connection type
 (``'binary'`` or ``'text'``).
+Or define custom WebSocket factory using ``Module['websocket']['factory']``. Factory
+is called with options param ``{addr, port, type, family, protocol}`` and
+must return WebSocket instance.
 
 Full POSIX Sockets over WebSocket Proxy Server
 ==============================================
diff --git a/src/lib/libsockfs.js b/src/lib/libsockfs.js
index 7ada365896fdc..24f267cd91664 100644
--- a/src/lib/libsockfs.js
+++ b/src/lib/libsockfs.js
@@ -172,6 +172,19 @@ addToLibrary({
             addr = result[1];
             port = parseInt(result[2], 10);
           }
+        } else if (typeof SOCKFS.websocketArgs["factory"] === "function") {
+          try {
+            ws = SOCKFS.websocketArgs["factory"]({
+              addr,
+              port,
+              type: sock.type,
+              family: sock.family,
+              protocol: sock.protocol
+            });
+            ws.binaryType = 'arraybuffer';
+          } catch (e) {
+            throw new FS.ErrnoError({{{ cDefs.EHOSTUNREACH }}});
+          }
         } else {
           // create the actual websocket object and connect
           try {

From b6e661ca13fac78c70b34dd0765e053f57a02156 Mon Sep 17 00:00:00 2001
From: Roman Turchin <roman@turch.in>
Date: Thu, 12 Jun 2025 21:54:23 +0200
Subject: [PATCH 2/2] wrap ws factory with expectToReceiveOnModule(websocket)

---
 src/lib/libsockfs.js | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/lib/libsockfs.js b/src/lib/libsockfs.js
index 24f267cd91664..14db4b71bcad0 100644
--- a/src/lib/libsockfs.js
+++ b/src/lib/libsockfs.js
@@ -172,7 +172,9 @@ addToLibrary({
             addr = result[1];
             port = parseInt(result[2], 10);
           }
-        } else if (typeof SOCKFS.websocketArgs["factory"] === "function") {
+        }
+#if expectToReceiveOnModule('websocket')
+        else if (typeof SOCKFS.websocketArgs["factory"] === "function") {
           try {
             ws = SOCKFS.websocketArgs["factory"]({
               addr,
@@ -185,7 +187,9 @@ addToLibrary({
           } catch (e) {
             throw new FS.ErrnoError({{{ cDefs.EHOSTUNREACH }}});
           }
-        } else {
+        }
+#endif
+        else {
           // create the actual websocket object and connect
           try {
             // The default value is 'ws://' the replace is needed because the compiler replaces '//' comments with '#'