diff --git a/src/lib/libcore.js b/src/lib/libcore.js
index d774ed139d044..f5f5f510e9d5f 100644
--- a/src/lib/libcore.js
+++ b/src/lib/libcore.js
@@ -2617,7 +2617,11 @@ function wrapSyscallFunction(x, library, isWasi) {
   post = handler + post;
 
   if (pre || post) {
-    t = modifyJSFunction(t, (args, body) => `function (${args}) {\n${pre}${body}${post}}\n`);
+    if (library[x + '__async']) {
+      t = modifyJSFunction(t, (args, body) => `async function (${args}) {\n${pre}${body}${post}}\n`);
+    } else {
+      t = modifyJSFunction(t, (args, body) => `function (${args}) {\n${pre}${body}${post}}\n`);
+    }
   }
 
   library[x] = eval('(' + t + ')');
diff --git a/src/lib/libeventloop.js b/src/lib/libeventloop.js
index a92f1415911d8..5565ab662e673 100644
--- a/src/lib/libeventloop.js
+++ b/src/lib/libeventloop.js
@@ -378,6 +378,9 @@ LibraryJSEventLoop = {
   emscripten_set_main_loop__deps: ['$setMainLoop'],
   emscripten_set_main_loop: (func, fps, simulateInfiniteLoop) => {
     var iterFunc = {{{ makeDynCall('v', 'func') }}};
+#if JSPI
+    iterFunc = WebAssembly.promising(iterFunc);
+#endif
     setMainLoop(iterFunc, fps, simulateInfiniteLoop);
   },
 
diff --git a/src/lib/libsockfs.js b/src/lib/libsockfs.js
index 493d2e749341f..99a9410128bd5 100644
--- a/src/lib/libsockfs.js
+++ b/src/lib/libsockfs.js
@@ -8,7 +8,7 @@ addToLibrary({
   $SOCKFS__postset: () => {
     addAtInit('SOCKFS.root = FS.mount(SOCKFS, {}, null);');
   },
-  $SOCKFS__deps: ['$FS'],
+  $SOCKFS__deps: ['$FS', '$DNS'],
   $SOCKFS: {
 #if expectToReceiveOnModule('websocket')
     websocketArgs: {},
@@ -69,6 +69,8 @@ addToLibrary({
         pending: [],
         recv_queue: [],
 #if SOCKET_WEBRTC
+#elif SOCKET_WEBTRANSPORT
+        sock_ops: SOCKFS.webtransport_sock_ops
 #else
         sock_ops: SOCKFS.websocket_sock_ops
 #endif
@@ -104,9 +106,9 @@ addToLibrary({
     },
     // node and stream ops are backend agnostic
     stream_ops: {
-      poll(stream) {
+      poll(stream, timeout) {
         var sock = stream.node.sock;
-        return sock.sock_ops.poll(sock);
+        return sock.sock_ops.poll(sock, timeout);
       },
       ioctl(stream, request, varargs) {
         var sock = stream.node.sock;
@@ -138,6 +140,288 @@ addToLibrary({
       return `socket[${SOCKFS.nextname.current++}]`;
     },
     // backend-specific stream ops
+#if SOCKET_WEBRTC
+#elif SOCKET_WEBTRANSPORT
+    webtransport_sock_ops: {
+      getSession(sock, addr, port) {
+        return sock.peers[`${addr}:${port}`];
+      },
+      initSession(sock, session, addr, port) {
+        sock.peers[`${addr}:${port}`] = session;
+
+        /* buffer writes before session is ready */
+        const outgoing = [];
+
+        session.write = (buffer) => {
+          outgoing.push(buffer);
+        };
+
+        /* prevent unhandled rejections before main loop */
+        session.ready.catch(() => {});
+        session.closed.catch(() => {});
+
+        (async () => {
+          try {
+            const sessionClosed = session.closed.then(
+              () => ({ done: true, value: null }),
+              (err) => { throw err; }
+            );
+
+            await session.ready;
+
+            const writer = session.datagrams.writable.getWriter();
+            const reader = session.datagrams.readable.getReader();
+            let first = true;
+
+            while (outgoing.length) {
+              writer.write(outgoing.shift());
+            }
+
+            session.write = (buffer) => {
+              writer.write(buffer).catch(e => console.warn(`Write failed for ${addr}:${port}`, e));
+            };
+
+            while (true) {
+              const { done, value } = await Promise.race([
+                reader.read(),
+                sessionClosed
+              ]);
+
+              if (done) {
+                break;
+              }
+
+              // handle the internal port identification message
+              if (first && value[0] === 0xff && value[1] === 0xff && value[2] === 0xff && value[3] === 0xff &&
+                           value[4] === 'p'  && value[5] === 'o'  && value[6] === 'r'  && value[7] === 't') {
+                // update cache key
+                delete sock.peers[`${addr}:${port}`];
+                port = parseInt(String.fromCharCode.apply(null, value.subarray(9)), 10);
+                sock.peers[`${addr}:${port}`] = session;
+              } else {
+                sock.recv_queue.push({ addr: addr, port: port, buffer: value });
+              }
+
+              if (sock.pendingPollResolve) {
+                sock.pendingPollResolve();
+              }
+
+              first = false;
+            }
+          } catch (e) {
+            console.error(`Session ${addr}:${port} terminated`, e);
+          } finally {
+            delete sock.peers[`${addr}:${port}`];
+          }
+        })();
+      },
+      newSession(sock, addr, port) {
+        let hostname = DNS.lookup_addr(addr);
+
+        if (!hostname) {
+          hostname = addr;
+        }
+
+        const session = new WebTransport(`https://${hostname}:${port}`);
+
+        SOCKFS.webtransport_sock_ops.initSession(sock, session, addr, port);
+
+        // send the original bound port number to the peer
+        if (sock.type === {{{ cDefs.SOCK_DGRAM }}} && typeof sock.sport != 'undefined') {
+          const msg = Uint8Array.from(`\xff\xff\xff\xffport ${sock.sport}\x00`, x => x.charCodeAt(0));
+          session.write(msg);
+        }
+
+        return session;
+      },
+      acceptSession(sock, session) {
+#if ENVIRONMENT_MAY_BE_NODE
+        const split = session.peerAddress.split(':');
+
+        const addr = split[0];
+        const port = parseInt(split[1], 10);
+
+        SOCKFS.webtransport_sock_ops.initSession(sock, session, addr, port);
+#endif
+      },
+      stopListenServer(sock) {
+#if ENVIRONMENT_MAY_BE_NODE
+        if (!ENVIRONMENT_IS_NODE) {
+          return;
+        }
+
+        if (!sock.h3) {
+          return;
+        }
+
+        sock.h3.stopServer();
+        sock.h3 = null;
+#endif
+      },
+      startListenServer(sock) {
+#if ENVIRONMENT_MAY_BE_NODE
+        if (!ENVIRONMENT_IS_NODE) {
+          return;
+        }
+
+        SOCKFS.webtransport_sock_ops.stopListenServer(sock);
+
+        sock.h3 = new Http3Server({
+          host: sock.saddr,
+          port: sock.sport,
+          secret: require('crypto').randomBytes(16).toString('hex'),
+          cert: Module['cert'],
+          privKey: Module['key']
+        });
+
+        (async () => {
+          try {
+            sock.h3.startServer();
+
+            await sock.h3.ready;
+
+            const sessionStream = await sock.h3.sessionStream('/');
+            const sessionReader = sessionStream.getReader();
+
+            while (true) {
+              const { done, value } = await sessionReader.read();
+
+              if (done) {
+                break;
+              }
+
+              SOCKFS.webtransport_sock_ops.acceptSession(sock, value);
+            }
+          } catch (e) {
+            sock.error = {{{ cDefs.EHOSTUNREACH }}};
+          } finally {
+            sock.h3 = null;
+          }
+        })();
+#endif
+      },
+
+      // actual sock ops
+#if ASYNCIFY
+      async poll(sock, timeout)
+#else
+      poll(sock, timeout)
+#endif
+      {
+        let mask = 0;
+
+        if (sock.type === {{{ cDefs.SOCK_STREAM }}}) {
+          throw new FS.ErrnoError({{{ cDefs.EOPNOTSUPP }}});
+        } else {
+#if ASYNCIFY
+          if (!sock.recv_queue.length) {
+            await new Promise((resolve, reject) => {
+              sock.pendingPromiseResolve = resolve;
+              setTimeout(resolve, timeout);
+            }).finally(() => {
+              sock.pendingPromiseResolve = null;
+            });
+          }
+#endif
+
+          if (sock.recv_queue.length) {
+            mask |= {{{ cDefs.POLLRDNORM }}} | {{{ cDefs.POLLIN }}};
+          }
+
+          /* always ready to write */
+          mask |= {{{ cDefs.POLLOUT }}};
+        }
+
+        return mask;
+      },
+      ioctl(sock, request, arg) {
+        switch (request) {
+          default:
+            return {{{ cDefs.EINVAL }}};
+        }
+      },
+      close(sock) {
+        for (const session of Object.values(sock.peers)) {
+          session.close();
+        }
+
+        SOCKFS.webtransport_sock_ops.stopListenServer(sock);
+
+        return 0;
+      },
+      bind(sock, addr, port) {
+        if (typeof sock.saddr !== 'undefined' || typeof sock.sport !== 'undefined') {
+          throw new FS.ErrnoError({{{ cDefs.EINVAL }}});  // already bound
+        }
+
+        sock.saddr = addr;
+        sock.sport = port;
+
+        if (sock.type === {{{ cDefs.SOCK_DGRAM }}}) {
+          SOCKFS.webtransport_sock_ops.startListenServer(sock);
+        } else {
+          throw new FS.ErrnoError({{{ cDefs.EOPNOTSUPP }}});
+        }
+      },
+      connect(sock, addr, port) {
+        if (sock.h3) {
+          throw new FS.ErrnoError({{{ cDefs.EOPNOTSUPP }}});
+        }
+
+        if (sock.type === {{{ cDefs.SOCK_STREAM }}}) {
+          throw new FS.ErrnoError({{{ cDefs.EOPNOTSUPP }}});
+        } else {
+          sock.daddr = addr;
+          sock.dport = port;
+        }
+      },
+      listen(sock, backlog) {
+        throw new FS.ErrnoError({{{ cDefs.EOPNOTSUPP }}});
+      },
+      sendmsg(sock, buffer, offset, length, addr, port) {
+        let session = null;
+
+        if (sock.type === {{{ cDefs.SOCK_STREAM }}}) {
+          throw new FS.ErrnoError({{{ cDefs.EOPNOTSUPP }}});
+        } else {
+          if (addr === undefined || port === undefined) {
+            addr = sock.daddr;
+            port = sock.dport;
+          }
+
+          session = SOCKFS.webtransport_sock_ops.getSession(sock, addr, port);
+
+          if (!session) {
+            session = SOCKFS.webtransport_sock_ops.newSession(sock, addr, port);
+          }
+        }
+
+        if (!session) {
+          throw new FS.ErrnoError({{{ cDefs.EDESTADDRREQ }}});
+        }
+
+        // copy off the buffer because write is async
+        buffer = buffer.slice(offset, offset + length);
+
+        session.write(buffer);
+
+        return length;
+      },
+      recvmsg(sock, length) {
+        if (sock.type === {{{ cDefs.SOCK_STREAM }}}) {
+          throw new FS.ErrnoError({{{ cDefs.EOPNOTSUPP }}});
+        }
+
+        const msg = sock.recv_queue.shift();
+
+        if (!msg) {
+          throw new FS.ErrnoError({{{ cDefs.EAGAIN }}});
+        }
+
+        return msg;
+      },
+    },
+#else
     websocket_sock_ops: {
       //
       // peers are a small wrapper around a WebSocket to help in
@@ -375,7 +659,7 @@ addToLibrary({
       //
       // actual sock ops
       //
-      poll(sock) {
+      poll(sock, timeout) {
         if (sock.type === {{{ cDefs.SOCK_STREAM }}} && sock.server) {
           // listen sockets should only say they're available for reading
           // if there are pending clients.
@@ -728,6 +1012,7 @@ addToLibrary({
         return res;
       }
     }
+#endif
   },
 
   /*
diff --git a/src/lib/libsyscall.js b/src/lib/libsyscall.js
index 3624805944ff8..eeef7d7e4faf6 100644
--- a/src/lib/libsyscall.js
+++ b/src/lib/libsyscall.js
@@ -484,11 +484,11 @@ var SyscallsLibrary = {
     var sock = getSocketFromFD(fd);
     if (!addr) {
       // send, no address provided
-      return FS.write(sock.stream, HEAP8, message, length);
+      return FS.write(sock.stream, HEAPU8, message, length);
     }
     var dest = getSocketAddress(addr, addr_len);
     // sendto an address
-    return sock.sock_ops.sendmsg(sock, HEAP8, message, length, dest.addr, dest.port);
+    return sock.sock_ops.sendmsg(sock, HEAPU8, message, length, dest.addr, dest.port);
   },
   __syscall_getsockopt__deps: ['$getSocketFromFD'],
   __syscall_getsockopt: (fd, level, optname, optval, optlen, d1) => {
@@ -606,7 +606,12 @@ var SyscallsLibrary = {
     '_emscripten_proxy_newselect',
 #endif
   ],
+#if ASYNCIFY
+  __syscall__newselect__async: true,
+  __syscall__newselect: async (nfds, readfds, writefds, exceptfds, timeoutInMillis) => {
+#else
   __syscall__newselect: (nfds, readfds, writefds, exceptfds, timeoutInMillis) => {
+#endif
 #if PTHREADS
     if (ENVIRONMENT_IS_PTHREAD) {
       return __emscripten_proxy_newselect(nfds,
@@ -631,7 +636,12 @@ var SyscallsLibrary = {
     '_emscripten_proxy_newselect_finish',
 #endif
   ],
+#if ASYNCIFY
+  _newselect_js__async: true,
+  _newselect_js: async (ctx, arg, nfds, readfds, writefds, exceptfds, timeoutInMillis) => {
+#else
   _newselect_js: (ctx, arg, nfds, readfds, writefds, exceptfds, timeoutInMillis) => {
+#endif
     // readfds are supported,
     // writefds checks socket open status
     // exceptfds are supported, although on web, such exceptional conditions never arise in web sockets
@@ -701,6 +711,11 @@ var SyscallsLibrary = {
 #endif
           return stream.stream_ops.poll(stream, timeoutInMillis);
         })();
+
+#if ASYNCIFY
+        /* poll is possibly a promise */
+        flags = await flags;
+#endif
       } else {
 #if ASSERTIONS
         if (timeoutInMillis != 0) warnOnce('non-zero select() timeout not supported: ' + timeoutInMillis)
diff --git a/src/modularize.js b/src/modularize.js
index b9a8414b2ce7c..21a2560f2aa85 100644
--- a/src/modularize.js
+++ b/src/modularize.js
@@ -11,6 +11,12 @@
 import source wasmModule from './{{{ WASM_BINARY_FILE }}}';
 #endif
 
+#if SOCKET_WEBTRANSPORT && ENVIRONMENT_MAY_BE_NODE
+#if EXPORT_ES6
+import { Http3Server, WebTransport } from '@fails-components/webtransport';
+#endif
+#endif
+
 #if ENVIRONMENT_MAY_BE_WEB && !EXPORT_ES6 && !(MINIMAL_RUNTIME && !PTHREADS)
 // Single threaded MINIMAL_RUNTIME programs do not need access to
 // document.currentScript, so a simple export declaration is enough.
diff --git a/src/settings.js b/src/settings.js
index 1ba3b7856b8da..1292d9fd2c4ab 100644
--- a/src/settings.js
+++ b/src/settings.js
@@ -402,6 +402,8 @@ var FS_DEBUG = false;
 // [link]
 var SOCKET_WEBRTC = false;
 
+var SOCKET_WEBTRANSPORT = false;
+
 // A string containing either a WebSocket URL prefix (ws:// or wss://) or a complete
 // RFC 6455 URL - "ws[s]:" "//" host [ ":" port ] path [ "?" query ].
 // In the (default) case of only a prefix being specified the URL will be constructed from