I have small application on nodejs + expressjs + socket.io and it works like a charm... mostly.
There is problem with flash socket policy server. Thing is that I cannot run socket policy server on port 843. If Flash Player cannot retrieve a master policy file from port 843, then it requests a socket policy file on the port where it is trying to connect. So the solution could be on 80 respond to normal http request (with express) and on the same port catch plain TCP connection with data <policy-file-request/>\0 and respond with policy. I was trying adapt this code but without luck.
How force express to respond with policy for TCP connection when <policy-file-request/>\0 is incoming and serve http response otherwise?
I don't know if this is possible with the socket.io Flash movie, but you could explicitly set a port to load the policy file from.
From the point of an ActionScript 3 developer you could do:
Security.loadPolicyFile("xmlsocket://example.com:10843");
socket = new FlashSocket("example.com:80");
This way it is possible to load the crossdomain.xml from a other port then your HTTP port or 843.
Related
I have NodeJs web service in based web socket. One of my file by the server side tries send xml to printer in local area network on ip address 192.168.1.5 but this ip is in my physical network not in area network by server side. When I open the web service on localhost it's work but when I open my service via network it's not work. How can I use web socket that nodejs app will send xml via TCP to another localhost in local area network using socket client just like me?
for example (my local area network):
localhost - 192.168.1.100
printer - 192.168.1.5
localhost (my physical computer) -> opening web service (NodeJS) on browser -> running script (service) -> sending xml via TCP to printer (192.168.1.5)
is this scenario possible?
You can't directly use webSocket or socket.io to send a plain TCP packet. webocket is its own protocol and socket.io runs on top of webSocket. It initiates a connection with an http request, uses it's own data format framing and its own security scheme. As such a webSocket client can only connect to a webSocket server or a socket.io client to a socket.io server, not to a plain TCP device.
You can use the Net module in node.js to make plain TCP connections. So, you can contact the printer directly from node.js if that would work.
But, you can't make plain TCP connections directly form a browser web page without using some sort of browser plug-in that has access to native code or without sending some sort of http or webSocket or socket.io request to a server and having the server contact the printer on your behalf (which would require server and printer to be on the same local network).
Is it possible to fetch NodeJS Socket server from web browser ?
I've create net server and i would like request this server from web client :
const server = net.createServer();
server.listen(SERVER_PORT);
I've try to fetch with ip and port, but no result.
Anyone have idea ?
This is not possible.
From web browser, you can only communicate through HTTP or WebSocket.
If you try to talk to a TCP server with the wrong protocol, it'll error out.
If you absolutly want your server to be a net TCP server, you can implement a server that communicate with your web app through a WebSocket and forward messages to your net server.
Otherwise, you could just do a WebSocket server, with socket.io for example.
Hope it helps,
regards
I am trying to create a multi room chat application in node.js using socket.io and express. I am confused between use of server port and websocket port. I understand server port is used by the client to connect to server. But not sure about use of websocket port.
Thanks & Regards..
webSockets can share the same port as your web server and this is a common configuration. The reason this works is because of how a webSocket establishes a connection (all webSocket connections are initiated with an HTTP request). It works like this:
Client makes an HTTP request to a web server with a header specifying that they want to "upgrade" to the webSocket protocol and sends a security-related header.
Web server sees the upgrade request and, if it has support enabled for webSocket connections, it will respond with a 101 request (switching protocols) and another security related header.
Client gets the accepted upgrade and both ends switch to the webSocket protocol and the original TCP socket that started out using the HTTP protocol is now using the webSocket protocol.
In this manner, the same port and webServer can be used for regular HTTP requests or webSocket connection requests.
For a chat application it is common to use a webSocket connection because it is a continuous connection that more easily allows the server to send information directly to the client which is often needed in a chat application.
To understand more about how a webSocket connection and server work, see this reference on MDN: Writing WebSocket servers which shows the step by step process for initiating a webSocket connection.
Server socket is used by server... that keeps listening to coming sockets request in a loop... and websocket sends a request to server socket and bound a connection between two devices...
If you have / want to have web clients, WebSocket is going to be required, because there is no access to 'regular' TCP (or UDP) sockets from browser-based JavaScript (and I assume you do not want Flash, SilverLight or Java Applets, in 2017). WebSocket is not special because of the port number, but it is special because of the protocol: a WebSocket connection starts as a regular HTTP connection, and protocol upgrade reconfigures it afterwards, it is designed for the browser-world, and even capable of traversing HTTP proxies. After establishing the connection, it provides a full-duplex, bi-directional message stream, very usable for chat applications.
And because of being a Web-thing, you could simply use port 80, if you are allowed to.
I'm making an app using node.js' express framework which serves both html content over http and uses websockets for a chat feature. I'm wondering how I can accomplish both at the same time. My idea is to use a different port for websocket connections (so http requests would come to port 3000 and websockets would connect on port 3001) but I don't know if that's a good solution. I'm especially worried about deployment to something like heroku and if I can specify different ports for my app.
I'm wondering how I can accomplish both at the same time.
The webSocket protocol is specially designed so it can run on the same port as your regular web server requests. So, you don't need a separate port in order to have both a web server and chat running using webSockets.
This works because a webSocket connection is always initiated with an http request that sets a few special headers. The receiving web server can then detect those special headers and know that this incoming http request is actually a request to initiate a webSocket connection. With a particular response, the client and server then agree to "upgrade" the connection and switch to the webSocket protocol. From that point on, that particular TCP connection uses the webSocket protocol.
Meanwhile any incoming http request that does not have the special webSocket headers on it is treated by your web server as just a regular http request. In this way, the same server and the same port can be used for both webSocket connections and regular http requests. No second port is needed.
Another advantage of this scheme is that the client can avoid the cross-origin issues that it would run into if it was trying to use a different port than the web page it was loaded from.
I'm especially worried about deployment to something like heroku and
if I can specify different ports for my app.
If you were to actually use two ports, then you would need to create two separate servers, one listening on each port since a given server can only listen on one port. In node.js, the two servers could both be in the same node.js app (making it easier to share data between them) or you could put them in completely separate node.js processes (your choice).
And, if you used multiple ports, you'd also have to support CORS so that the browser would be allowed to connect to the separate port (to avoid same-origin restrictions).
I have ExspressJS app run with Socket.io, due to firewall issues with higher port for SIO i want to switch that both will work on port 80.
Found this small article and on my dev machine it's look working good.
My question is, is it really goo to do that? is it a good practice? if not why?
Please advise.
It makes absolute sense to run socket.io and your web server on the same port.
The webSocket protocol (which socket.io is based on) is specifically designed for this to be the primary way that socket.io is used for a bunch of reasons including same-origin permissions and client and server firewall routing of port 80.
In case you didn't realize it, every socket.io connection starts with an HTTP request to a specific route and then once the initial handshake between client and server has been confirmed, then the protocol is "upgraded" from HTTP to webSocket. Because all socket.io connections connect in on a very specific route, all other HTTP connections can easily be separated out and be treated by your web server as regular web requests.