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Comment by _urga | Hacker News Reader

FileSystemAPI support in Firefox, and the ability to tell the operating system to open a file stored with FileSystemAPI using the default registered native application (it must be possible to get notifications when this file changes, for syncing to the server). This would enable the DropBox use-case, where a user could drag an excel file into a web app, click a link in the web app to edit it with Microsoft Excel, and then press Save in Excel, and the web app would sync a diff with the server.

Add a Javascript API to enable a web app to open a TCP socket (as opposed to WebSocket) with the origin server.

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the ability to tell the operating system to open a file stored with FileSystemAPI using the default registered native application (it must be possible to get notifications when this file changes, for syncing to the server).

This is a seriously scary concept. It has all the same dangers as the automatic-file-opening did in Outlook.

It can probably be done securely, but wow, that's not an easy problem.

For sure, it's difficult. As you say, it probably can be done securely. It certainly needs to be done to provide users with a bridge for moving data from file systems into web apps and back and manipulating data from both sides of the bridge. It may require a special privilege, and in that case, for example for a trusted web app, it need be no more scary than a browser prompt: "allow this web application to open 'mydata.xls' in Excel?" with a "remember my choice for all files of this type from now on".

What use cases for TCP do you envision where WebSocket won't be sufficient? It is quite possible to speak standard protocols over WebSocket that are typically spoken over TCP.

TCP does not need the upgrade event, handshake etc. TCP is not limited by the WebSocket spec. TCP requires no additional server-side infrastructure.

Last thing first: TCP requires a listening server. WebSocket requires a listening server. There is not inherently more infrastructure required.

The handshake and HTTP upgrade are there for a reason. Connecting out from web applications with straight TCP breaks the web security model. After the handshake, you can treat WebSocket binary frames as if they were a TCP byte stream. Speak any protocol you want to.

Anything you can do with TCP you can do with WebSocket. The only exception is that you cannot connect to a listening server that does not expect the WebSocket handshake. That is intentional! In fact, that is the reason for the WebSocket handshake.

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