Fix file upload widget (fixes to sending binary data to kernel)

src/kernels/raw/session/rawSocket.node.ts

@@ -258,7 +258,17 @@ export class RawSocket implements IWebSocketLike, IKernelSocket, IDisposable {
 
             this.sendChain = this.sendChain
                 .then(() => Promise.all(this.sendHooks.map((s) => s(hookData, noop))))
-                .then(() => this.postToSocket(msg.channel, data));
+                .then(async () => {
+                    try {
+                        await this.postToSocket(msg.channel, data);
+                    } catch (ex) {
+                        traceError(`Failed to write data to the kernel channel ${msg.channel}`, data, ex);
+                        // No point throwing this error, as that would mean nothing else works from here on end.
+                        // Lets ignore this error but log it and then continue
+                        // Hopefully users will file bugs and we can fix this (based on the error message).
+                        // throw ex;
+                    }
+                });
         } else {
             this.sendChain = this.sendChain.then(() => {
                 this.postToSocket(msg.channel, data);

src/notebooks/controllers/ipywidgets/message/ipyWidgetMessageDispatcher.ts

@@ -376,7 +376,17 @@ export class IPyWidgetMessageDispatcher implements IIPyWidgetMessageDispatcher {
         }
         while (this.pendingMessages.length) {
             try {
-                const msg = JSON.parse(this.pendingMessages[0]) as KernelMessage.IMessage;
+                const message = this.pendingMessages[0];
+                const msg: KernelMessage.IMessage =
+                    typeof message === 'string' ? JSON.parse(message) : this.deserialize(message);
+                if (msg.buffers?.length) {
+                    msg.buffers = msg.buffers.map((buffer) => {
+                        if (buffer instanceof DataView) {
+                            return buffer.buffer;
+                        }
+                        return buffer;
+                    });
+                }
                 if (msg.channel === 'control') {
                     this.kernel.session.kernel!.sendControlMessage(msg as unknown as KernelMessage.IControlMessage);
                 } else {