Setting up a websocket on Apache?

 

So I'm doing some research on websockets, and I have a few questions I can't seem to find a definitive answer for:

  • How can I set up a web socket on my Linux server? Is there an Apache module? Would I have to use 3rd-party PHP code or similar?

  • Are there any kinds of drawbacks to the method described in question 1 that I should be aware of other than browser compatibility?

  • How could I "upgrade" my websocket installation to a secure websocket installation (ws:// to wss://)? Would this be made easier or more difficult if SSL was already set up on my Apache server?

  • Is there any language I could use to connect to my web socket other than JavaScript?

  • What is the default request method for a web socket?

    • I can't answer all questions, but I will do my best.

    As you already know, WS is only a persistent full-duplex TCP connection with framed messages where the initial handshaking is HTTP-like. You need some server that's listening for incoming WS requests and that binds a handler to them.

    Now it might be possible with Apache HTTP Server, and I've seen some examples, but there's no official support and it gets complicated. What would Apache do? Where would be your handler? There's a module that forwards incoming WS requests to an external shared library, but this is not necessary with the other great tools to work with WS.

    WS server trends now include: Autobahn (Python) and Socket.IO (Node.js = JavaScript on the server). The latter also supports other hackish "persistent" connections like long polling and all the COMET stuff. There are other little known WS server frameworks like Ratchet (PHP, if you're only familiar with that).

    In any case, you will need to listen on a port, and of course that port cannot be the same as the Apache HTTP Server already running on your machine (default = 80). You could use something like 8080, but even if this particular one is a popular choice, some firewalls might still block it since it's not supposed to be Web traffic. This is why many people choose 443, which is the HTTP Secure port that, for obvious reasons, firewalls do not block. If you're not using SSL, you can use 80 for HTTP and 443 for WS. The WS server doesn't need to be secure; we're just using the port.

    Edit : According to Iharob Al Asimi, the previous paragraph is wrong. I have no time to investigate this, so please see his work for more details.

    About the protocol, as Wikipedia shows, it looks like this:

    Client sends: 

    GET /mychat HTTP/1.1
Host: server.example.com
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: x3JJHMbDL1EzLkh9GBhXDw==
Sec-WebSocket-Protocol: chat
Sec-WebSocket-Version: 13
Origin: http://example.com

    Server replies: 

    HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: HSmrc0sMlYUkAGmm5OPpG2HaGWk=
Sec-WebSocket-Protocol: chat

    and keeps the connection alive. If you can implement this handshaking and the basic message framing (encapsulating each message with a small header describing it), then you can use any client-side language you want. JavaScript is only used in Web browsers because it's built-in.

    As you can see, the default "request method" is an initial HTTP GET, although this is not really HTTP and looses everything in common with HTTP after this handshaking. I guess servers that do not support 

    Upgrade: websocket
Connection: Upgrade

    will reply with an error or with a page content.

    The new version 2.4 of Apache HTTP Server has a module called mod_proxy_wstunnel which is a websocket proxy.

    http://httpd.apache.org/docs/2.4/mod/mod_proxy_wstunnel.html

    链接地址: http://www.djcxy.com/p/44716.html

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