Develop Reference

Phoenix channels with Android client

I'm trying to create a websocket connection to my Phoenix app from an Android client. I'm trying to use this library but I'm running into this issue and I'm unable to successfully join a channel.
Upon reviewing the source code of the above java phoenix client library, it looks like the initial request from the client to connect to the socket is made with http schema and not ws (the source code explicitly changes the provided url to make sure it always uses http). It's not clear to me how this would work without additional configuration in my Phoenix app: if a socket connect request is made to http://localhost:4000/socket, the request will fail because there is no route for /socket when the schema is http.
There's nothing in the library docs that says any additional config is required in my Phoenix app to make this work, but I don't see how it could work for the reason stated above.
Does a Phoenix app have built in handling for the connection upgrade, etc, required on handshake as specified here?
As a note, I have no issues making websocket connections from my javascript web client to my Phoenix backend.
Any suggestions are appreciated!

Have you tried using the default path for a channel http://localhost:4000/socket/websocket ?

Client (Mobile) how to intercept and modify http response

I am Android developer, my application uses a bunch of http REST calls and it gets responses from servers. I use Charles to inspect the data (so I have to install Charles certificate onto my device so that https traffic can be read by myself).
Are there any tools out there like Charles that will allow me to modfiy that response packet before sending to the client ??

Depending on what exactly you want to modify, Charles' inbuilt Rewrite Tool might be what you are looking for. You find it in the Tools menu. You can specify which requests shall be modified by protocol, host, port, path and query, and you have the following modification options:
Add, modify, remove headers (request and response)
Modify Host, Path, URL, Response Status
Add, modify, remove Query Parameters
Modify body (request and response)
Another option is Fiddler. Like Charles it can be configured as a proxy for android, decrypt HTTPS traffic and modify request and response.

Charles itself has the functionality. Follow the steps:
enable break points by right click on individual request or a path
Before sending the request, Charles will give you a change to edit it. See below. Click "edit request" to fill in whatever you want and click "execute" to send the request.
Before posting the result back to your mobile phone, you have a change to edit the content. See below.

You may try OWASP ZAP or Burp Suite. OWASP ZAP is completely free and provides a number of features.

See also Android : Capturing HTTP Requests with non-rooted android device.
I've recently tested HTTP Toolkit on Android emulator. It works and allows to capture and edit response from a server. Some functions are paid (in Pro version). Requires root priviledges on real devices.
You can also use Burp Suite or Fiddler.

Why would some HTTPS requests fail to decrypt on Fiddler, while some works ?

Scenario: I am trying to debug an Android app by proxying requests through Fiddler.
I got FiddlerRoot certificate installed on the Android device, and the SSL decryption works for most requests, but for other requests I can only see the HTTPS Connect, and nothing else in the Fiddler log. I think it might be image requests over SSL that fails to decrypt.
I have double-checked that "Hide images" is off, etc. Images retrieved are hosted on another domain than the main API the app talks to.
What could cause this behaviour ? And how do I get the image requests to show in Fiddler ?
I am using the latest Fiddler4.

There are plenty of tutorials on how you can intercept HTTP(s) traffic from Android using Fiddler.
Try this one: http://docs.telerik.com/fiddler/configure-fiddler/tasks/configureforandroid
However, it will fail when you try to intercept and decrypt Android SSL traffic coming from an application, and not from a browser.
It might be that the application uses a certificate pinning – and you are probably cannot decipher this connection. Lost cause!
But more probably, the reason is a bug in the HttpsUrlConnection pipeline implementation.
To solve the issue, please proceed with the following steps:
In Fiddler click "Rules->Customize Rules";
Find function OnBeforeResponse in the script
Add following code to the function body:
if (oSession.oRequest["User-Agent"].indexOf("Dalvik") > -1 &&
oSession.HTTPMethodIs("CONNECT")) {
oSession.oResponse.headers["Connection"] = "Keep-Alive";
}
Save the file and restart Fiddler.

Internet Connection Problems over Cellular

We have discovered a strange bug in on of our Android apps in that the app cannot connect to the internet over cellular on certain Android Models/Mobile Networks (connecting via WiFi works perfectly). The URL which the app is trying is to reach is however accessible using the device's normal browser, which rules out the URL being blocked upstream. Any ideas what could be causing this would be appreciated please.

which rules out the URL being blocked upstream
Not necessarily. As one of the commenters pointed out, you do not indicate how you are using this URL in your app. If this is an HTTP request, and it works in a browser but not your app, try changing the User-Agent HTTP header of your request to match the one from the browser.

You have provided no error log, but from experience I have run into a few inconsistencies when connecting to a server.
Using HttpsUrlConnection a SNI header is set on HoneyComb and above but not on previous versions, which can alter how the server responds. To add to this there are some general SSL handling inconsistencies between API levels, such as handling of wildcard domains in a certificate is buggy in some api levels.
Second some phones/api levels add a header to HttpUrlConnection requests that specifies time the request was sent like so:
X-Android-Sent-Millis=1353085024868
Some servers seem to use these headers to detect mobile traffic and alter the response.

I had problems when using a dual-simcard. Do you have more devices connected? Try to shut them down.

How to debug http calls on Android devices?

I'm writing a Lovefilm client for Android, and it's not going too badly except I keep having problems with the remote calls to retrieve data from the API.
Does anyone have any tips for debugging remote calls like this? Can I tcpdump on Android or is there a native way of doing it?
For example, I'm using the Scribe-java library for OAuth to access the Lovefilm API, I can authenticate find and retrieve a list of films on the users account fine when the device is running Gingerbread, but trying to retrieve the accessToken on Froyo causes a blank response & and apparent response code of -1, I'd like to be able to see what's going on under the cvers their.
Another example I'd like to be able to the raw http for is trying to run a search, I get and IOError that says "Received authentication challenge is null"

I've used Fiddler (http-proxy for debugging http calls) with the android emulator in these cases. Just start the proxy, and start the emulator with the correct proxy address (-http-proxy ).

Fiddler is the most useful option. On the emulator #Scythe answer will work, but on a real device you will need to set the proxy in the Apache Http Client. The following code will do that:
HttpHost proxy = new HttpHost("youripaddr", 8888);
params.setParameter(ConnRoutePNames.DEFAULT_PROXY, proxy);
If you are using https, fiddler is not so useful. In that case can enable the build in logging support in Apache Http Client. The following code does that:
Headers only:
java.util.logging.Logger apacheHeaderLog = java.util.logging.Logger.getLogger("org.apache.http.headers");
apacheHeaderLog.setLevel(java.util.logging.Level.FINEST);
Headers & Wire:
java.util.logging.Logger apacheWireLog = java.util.logging.Logger.getLogger("org.apache.http.wire");
apacheWireLog.setLevel(java.util.logging.Level.FINEST);
Note that this will have to have a java.util.logging Handler configured at finest level and the default handler is configured to log to logcat, which will filter DEBUG (finest) entries by default.

If your system can share the wi-fi connection you should be able to route packets from any device through your system and then using wireshark you can get monitor your calls or get a tcpdump.
Also , and more importantly , it would be best if you log your network calls and responses as suggested by #Matthew
Windows 7 wi-fi connection sharing : http://www.winsupersite.com/article/faqtip/windows-7-tip-of-the-week-use-wireless-hosted-networking-to-share-an-internet-connection-wirelessly.aspx

Since I always run into similar troubles and it seems a lot of people having the same issues over and over again I wrote up a quick tutorial for debugging client-server communication by using netcat and cURL.
That of course only works for the simplified case that you always 'fake' on side of the connection.
For eavesdropping you can use tools like tcpdump or Wireshark. Which will definitely be easier if you're able to run the server instance directly on your local machine.

Stetho is a great tool from FB which helps in debugging android Apps. You can have access to local data and have a check on your network using this.
http://facebook.github.io/stetho/