Develop Reference

What sort of message does Snapd's API expect?

Snapd has documentation on a REST API.
I'm able to connect to the socket from C# using the following
var snapSocket = new Socket(AddressFamily.Unix, SocketType.Stream, ProtocolType.IP);
var snapEndpoint = new UnixEndPoint("/run/snapd.socket");
snapSocket.Connect(snapEndpoint);
var req = Encoding.ASCII.GetBytes("GET /v2/system-info HTTP/1.1");
snapSocket.Send(req, req.Length, 0);
var bytesReceived = new byte[256];
var bytes = 0;
var response = "";
do
{
bytes = snapSocket.Receive(bytesReceived, bytesReceived.Length, 0);
response = response + Encoding.ASCII.GetString(bytesReceived, 0, bytes);
} while (bytes > 0);
Console.WriteLine(response);
But everything halts at snapSocket.Receive - a response is never sent. I suspect that there's something wrong with the message that I'm sending it.

It turns out that it expects a standard HTTP request, which means a Host: line, a Connection: Close line, and two \ns at the very end are required.
The documentation's following claim...
While it is expected to allow clients to connect using HTTPS over a TCP socket, at this point only a UNIX socket is supported.
... is meant only to imply that HTTPS and TCP do not work yet - HTTP is currently the valid request format even when using the UNIX Socket.

I am not fluent in C# at all, but maybe this python snippet can help lead into a solution:
import requests_unixsocket
session = requests_unixsocket.Session()
r = session.get('http+unix://%2Frun%2Fsnapd.socket/v2/snaps')
r.raise_for_status()
r.json()

HttpClient accessing a socket application

I started down the path of using HttpClient as I thought the service I was accessing is a REST service. Turns out it's a JSON service running on port 80 but is a socket application.
The HttpClient opens the remote port but when it sends the JSON request it never gets a response. I was having the hardest time getting fiddler to get a response back as well. But I was able to get wget and curl to send/receiving a response. That's when I talked to the original developer and he mentioned that it wasn't a true "REST" service, but just a socket application that sends/receives JSON.
Is there something I can do to tweak HttpClient to access a socket application or am I going to have to take a step back and use WebSockets?
This is the test code that sends/receives the JSON packet.
private async Task ProcessZone(string szIPAddress)
{
string responseData = string.Empty;
Uri baseAddress = new Uri(#"http://" + szIPAddress + "/player");
try
{
using (var httpClient = new HttpClient { BaseAddress = baseAddress })
{
var _req = new SendRequest();
_req.id = "rec-100";
_req.url = "/stable/av/";
_req.method = "browse";
var _json = JsonConvert.SerializeObject(_req);
using (var content = new StringContent(_json,Encoding.UTF8, "application/json"))
{
using (var response = await httpClient.PostAsync(baseAddress, content))
{
responseData = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
}
}
}
var _Response = JsonConvert.DeserializeObject<Response>(responseData);
var item = new ZoneInfo();
item.szIPAddress = szIPAddress;
item.szZoneName = _Response.result.item.title;
lstZones.Add(item);
}
catch (Exception ex)
{
Debug.WriteLine(ex.Message);
}
}
private async Task ProcessZones()
{
foreach (var item in ZoneSearch)
{
await ProcessZone(item.IPAddress);
}
}
The connection hangs on this line:
using (var response = await httpClient.PostAsync(baseAddress, content))
I should also mention that the code above does work fine on a true rest service...

That's when I talked to the original developer and he mentioned that it wasn't a true "REST" service, but just a socket application that sends/receives JSON.
Knowing the protocol is the first step towards making a working client.
Is there something I can do to tweak HttpClient to access a socket application or am I going to have to take a step back and use WebSockets?
Neither, unfortunately. HttpClient - as the name implies - only works with HTTP services. Since the server is not an HTTP server, it won't work with HttpClient. WebSockets have a rather confusing name, since they are not raw sockets but instead use the WebSocket protocol, which require an HTTP handshake to set up. Since the server is not an HTTP/WebSocket server, it won't work with WebSockets.
Your only choices are to either pressure the developer to write a real REST service (which makes your job orders of magnitude easier), or use raw sockets (e.g., Socket). Correctly using raw sockets is extremely difficult, so I recommend you pressure the developer to write a REST service like the entire rest of the world does today.

How to send messages from server to a specific client

I am using WebSockets and trying to set up a code base for my server-client. I know how to send messages from client to server and I also know how to listen those messages from the server side.
However, how can I send a message back to a client ?
// here is the _clientSocket that I accepted
_clientSocket = _serverSocket.Accept();
int received = _clientSocket.Receive(_buffer, 0, _buffer.Length,
SocketFlags.None);
// here is the message I got from the client
string receivedMsg = Encoding.ASCII.GetString(_buffer);
if (receivedMsg == "1")
//TO DO: send back to client "This is a test message from server".

Basically you have to use the SendAsync method:
var sendbuffer = new ArraySegment<byte>(Encoding.UTF8.GetBytes("Whatever text you want to send"));
await socket.SendAsync(sendbuffer , WebSocketMessageType.Text, true, CancellationToken.None)
.ConfigureAwait(false);
Take a look at this example: https://stackoverflow.com/a/26274839/307976

You have to call:
_clientsocket.Send(...);

Can't get entire response from proxy C#

I'm building a small HTTP proxy that runs between the browser and squid proxy. The browser sends the HTTP request to my proxy that redirects it to the squid proxy, then my application gets the response from the squid proxy and returns it back to the browser.
the problem is that i can't get the full response from the proxy, i get HTTP 200 OK ... (just the response header), but with out the body then i have to call receive method another time to get the body. but if i debug my code (which make the application slower) it get all the response (response header and body)
is there any propriety in the TCPClass that indicates to me that the remote server still have data to send to me ?
here is my code :
static void Main(string[] args)
{
int ServerPort = 8888;
IPAddress localHost = new IPAddress(0x0100007f);
TcpListener listener = new TcpListener(localHost,ServerPort);
listener.Start();
while(true)
{
string requestString = "";
String respenseString = "";
TcpClient application = listener.AcceptTcpClient();
string source = application.Client.RemoteEndPoint.ToString();
byte[] dataFromApp = new byte[application.ReceiveBufferSize];
application.Client.Receive(dataFromApp);
TcpClient tunnel = new TcpClient("127.0.0.1",8080);
tunnel.Client.Send(dataFromApp);
while (tunnel.Client.Connected ==true)
{
if(tunnel.Available != 0)
{
byte[] responseFromProxy = new byte[tunnel.ReceiveBufferSize];
tunnel.Client.Receive(responseFromProxy);
respenseString += Encoding.UTF8.GetString(responseFromProxy);
}
else
{
break;
}
}
application.Client.Send(Encoding.UTF8.GetBytes(respenseString));
}

You should check the return value of tunnel.Client.Receive and application.Client.Receive. Receive doesn't gurantee that it will read dataFromApp.Length bytes
REMARKS: The Receive method reads data into the buffer parameter and returns the number of bytes successfully read
PS: You may also want to try FiddlerCore to write an Http Proxy

There is no "there are N bytes remaining for this message" property on a socket, because a TCP socket is streaming: it sends and receives bytes, not messages.
HTTP defines messages, and if you are implementing an HTTP proxy, you should be familiar with the HTTP 1.1 RFC. There are various ways to determine the lenght of an HTTP message, all of which you have to implement to make sure you can successfully receive and send HTTP messages.

Thanks guys
I've done it :
while (tunnel.Client.Receive(oneByte) != 0)
{
byte[] responseFromProxy = new byte[tunnel.Available];
tunnel.Client.Receive(responseFromProxy);
application.Client.Send(oneByte);
application.Client.Send(responseFromProxy);
}

how to receive server push data in c#?

I am writing a program. my program receive data from a server through HTTP protocol. the data will be pushed by server to my program.
I tried to use WebRequest, but only received one session of data.
How can i keep the connection alive, to receive the data from server continuosly,
Any help is appreciated.
the following is the SDK document:
Under the authorization of GUEST or ADMIN, it is possible to get the series of live images
(Server push). To get the images, send the request to “/liveimg.cgi?serverpush=1” as shown
in the Figure. 2-1-1.
When the camera receives the above request from the client, it sends the return as shown
in the Figure. 2-2.
Each JPEG data is separated by “--myboundary”, and “image/jpeg” is returned as
“Content-Type” header, after “--myboundary”. For “Content-Length” header, it returns the
number of bytes in the --myboundary data (excluding “--myboundary”, each header, and
\r\n as delimiter). After the “Content-Length” header and “\r\n” (delimiter), the actual
data will be sent.
This data transmission will continue until the client stop the connection (disconnect), or
some network error occurs.
int len;
string uri = #"http://192.168.0.2/liveimg.cgi?serverpush=1";
HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(uri);
req.Credentials = new NetworkCredential("admin", "admin");
req.KeepAlive = true;
string line = "";
HttpWebResponse reply = (HttpWebResponse)req.GetResponse();
Stream stream = reply.GetResponseStream();
System.Diagnostics.Debug.WriteLine(reply.ContentType);
StreamReader reader = new StreamReader(stream);
do
{
line = reader.ReadLine();
System.Diagnostics.Debug.WriteLine(line);
System.Threading.Thread.Sleep(300);
} while (line.Length>0);

You can keep an HTTP connection open for an extended period of time, if the server supports doing so. (As already mentioned, this will significantly limit the number of simultaneous users you can support.)
The server will need to be set Response.Buffer=false, and have an extended ScriptTimeout (I'm assuming your using ASP.NET on the server side). Once you do that, your page can keep sending Response.Write data as needed until whatever it is doing is done.
Your client will need to process the incoming Response before the connection is complete rather than blocking for the complete response.

You may want to take a look at StreamHub Push Server - its a popular Comet server and has an .NET Client SDK which allows you to receive real-time push updates in C# (or VB / C++).

If I'm understanding you correctly, your server is going to respond to some event by sending data to your client outside of the client making a request/response. Is this correct? If so, I wouldn't recommend trying to keep the connection open unless you have a very small number of clients -- there are a limited number of connections available, so keeping them open may rapidly result in an exception.
Probably the easiest solution would be to have the clients poll periodically for new data. This would allow you to use a simple server and you'd only have to code a thread on the client to request any changes or new work once every minute or thirty seconds or whatever your optimal time period is.
If you truly want to have the server notify the clients proactively, without them polling, then you'll have to do something other than a simple web server -- and you'll also have to code and configure the client to accept incoming requests. This may be difficult if your clients are running behind firewalls and such. If you go this route, WCF is probably your best choice, as it will allow you to configure server and client appropriately.

You need to get a cookie from IP cam and include that cookie in header of your next HttpWebRequest. Otherways it will always try to redirect you to "index.html".
Here is how you can do it...
BitmapObject is a class that serves as a container for Jpeg image, current date and eventual error text. Once a connection is established it will pool an image every 200 ms. Same should be applicable for continuous image stream obtained through "serverpush".
public void Connect()
{
try
{
request = (HttpWebRequest)WebRequest.Create("Http://192.168.0.2/index.html");
request.Credentials = new NetworkCredential(UserName,Password);
request.Method = "GET";
response = (HttpWebResponse)request.GetResponse();
WebHeaderCollection headers = response.Headers;
Cookie = headers["Set-Cookie"];//get cookie
GetImage(null);
}
catch (Exception ex)
{
BitmapObject bitmap = new BitmapObject(Properties.Resources.Off,DateTime.Now);
bitmap.Error = ex.Message;
onImageReady(bitmap);
}
}
private Stream GetStream()
{
Stream s = null;
try
{
request = (HttpWebRequest)WebRequest.Create("http://192.168.0.2/liveimg.cgi");
if (!Anonimous)
request.Credentials = new NetworkCredential(UserName, Password);
request.Method = "GET";
request.KeepAlive = KeepAlive;
request.Headers.Add(HttpRequestHeader.Cookie, Cookie);
response = (HttpWebResponse)request.GetResponse();
s = response.GetResponseStream();
}
catch (Exception ex)
{
BitmapObject bitmap = new BitmapObject(Properties.Resources.Off,DateTime.Now);
bitmap.Error = ex.Message;
onImageReady(bitmap);
}
return s;
}
public void GetImage(Object o)
{
BitmapObject bitmap = null;
stream = GetStream();
DateTime CurrTime = DateTime.Now;
try
{
bitmap = new BitmapObject(new Bitmap(stream),CurrTime);
if (timer == null)//System.Threading.Timer
timer = new Timer(new TimerCallback(GetImage), null, 200, 200);
}
catch (Exception ex)
{
bitmap = new BitmapObject(Properties.Resources.Off, CurrTime);
bitmap.Error = ex.Message;
}
finally
{
stream.Flush();
stream.Close();
}
onImageReady(bitmap);
}

If you are using a standard web server, it will never push anything to you - your client will have to periodically pull from it instead.
To really get server push data you have to build such server yourself.