Develop Reference

TcpListener AcceptSocket() accepts two connections for each single GET request

I have this web server program up and running, using TcpListener. The problem is that for each get request made through web browser (or chrome Postman extension), it captures two requests.
namespace Server
{
class WebServer2
{
private TcpListener listener;
private int port = 8080;
public WebServer2()
{
try
{
listener = new TcpListener(IPAddress.Parse("127.0.0.1"), port);
listener.Start();
Console.WriteLine("Listening...");
//start the thread which calls the method 'StartListen'
Thread th = new Thread(new ThreadStart(StartListen));
th.Start();
}
catch (Exception e)
{
Console.WriteLine("An Exception Occurred While Listening: " + e.ToString());
}
}
//Recieve Request
public void StartListen()
{
int iStartPos = 0;
String sRequest;
String sRequestedFile;
String sResponse = "";
while (true)
{
//Accept a new connection
Socket socket = listener.AcceptSocket();
if (socket.Connected)
{
Console.WriteLine("\nClient Connected");
Console.WriteLine("----------------");
//Receive data from the client
Byte[] bReceive = new Byte[1024];
int i = socket.Receive(bReceive, bReceive.Length, 0);
//Convert Byte to String
string sBuffer = Encoding.ASCII.GetString(bReceive);
//Only GET Request is accepted
if (sBuffer.Substring(0, 3) != "GET")
{
Console.WriteLine("Not a Get Request.");
socket.Close();
continue;
}
// Look for HTTP request
iStartPos = sBuffer.IndexOf("HTTP", 1);
// Get the HTTP text and version e.g. it will return "HTTP/1.1"
string sHttpVersion = sBuffer.Substring(iStartPos, 8);
// Extract the Requested Type and Requested file/directory
sRequest = sBuffer.Substring(0, iStartPos - 1);
//If file name not provided
if (sRequest.IndexOf(".") < 1)
{
Console.WriteLine("File name not Provided!");
socket.Close();
continue;
}
//Extract the requested file name
iStartPos = sRequest.LastIndexOf("/") + 1;
sRequestedFile = sRequest.Substring(iStartPos);
Console.WriteLine("Requested File: " + sRequestedFile);
int iTotBytes = 0;
sResponse = "";
FileStream fs = new FileStream(sRequestedFile, FileMode.Open, FileAccess.Read, FileShare.Read);
BinaryReader reader = new BinaryReader(fs);
byte[] bytes = new byte[fs.Length];
int read;
while ((read = reader.Read(bytes, 0, bytes.Length)) != 0)
{
// Read from the file and write the data to the network
sResponse = sResponse + Encoding.ASCII.GetString(bytes, 0, read);
iTotBytes = iTotBytes + read;
}
reader.Close();
fs.Close();
SendHeader(sHttpVersion, "text/html", iTotBytes, " 200 OK", ref socket);
SendToBrowser(bytes, ref socket);
socket.Send(bytes, bytes.Length, 0);
socket.Close();
}
}
}
// Overloaded Function, takes string, convert to bytes and calls
// overloaded sendToBrowserFunction.
public void SendToBrowser(String sData, ref Socket socket)
{
SendToBrowser(Encoding.ASCII.GetBytes(sData), ref socket);
}
/// Sends data to the browser (client)
public void SendToBrowser(Byte[] bSendData, ref Socket socket)
{
int numBytes = 0;
try
{
if (socket.Connected)
{
if ((numBytes = socket.Send(bSendData, bSendData.Length, 0)) == -1)
Console.WriteLine("Socket Error");
}
else
Console.WriteLine("Connection Dropped!");
}
catch (Exception e)
{
Console.WriteLine("Error: {0} ", e);
}
}
// This function send the Header Information to the client (Browser)
public void SendHeader(string sHttpVersion, string sMIMEHeader, int iTotBytes, string sStatusCode, ref Socket socket)
{
String sBuffer = "";
Byte[] bSendData;
if (sStatusCode.Equals("404") || sStatusCode.Equals("400"))
{
sBuffer = sBuffer + sHttpVersion + sStatusCode + "\r\n";
sBuffer = sBuffer + "Server: MyServer\r\n";
sBuffer = sBuffer + "Content-Length: " + 0 + "\r\n\r\n";
bSendData = Encoding.ASCII.GetBytes(sBuffer);
SendToBrowser(bSendData, ref socket);
}
else
{
sBuffer = sBuffer + sHttpVersion + sStatusCode + "\r\n";
sBuffer = sBuffer + "Server: MyServer\r\n";
sBuffer = sBuffer + "Content-Type: " + sMIMEHeader + "\r\n";
sBuffer = sBuffer + "Accept-Ranges: bytes\r\n";
sBuffer = sBuffer + "Content-Length: " + iTotBytes + "\r\n\r\n";
bSendData = Encoding.ASCII.GetBytes(sBuffer);
SendToBrowser(bSendData, ref socket);
}
}
}
}
Single request made by chrome against http://localhost:8080/page1.html
Request made by Postman Extension
The funny thing is, everything works find when I send request through my client program (using TcpClient).

I tested your server and got similar results:
Chrome automatically asks for a favicon.ico file for every request. This generates the extra GET request to your server.
Firefox doesn't do this and simply generates one request per refresh.
Then there is a second problem I experienced, which is the one in your Postman screenshot.
Chrome (including the Postman Extension running inside it) reconnects
without sending anything, so the server "hangs" until you get a
response filled with \0 (nul-characters).
This is part of Chrome's prediction service to load subsequent requests faster. You could disable this behavior under Settings (advanced) > Privacy:
In your server implementation, this results in the "Not a Get Request" output if no subsequent GET request follows (instead, Chrome sends \0 to signal its not sending anything anyway).
Note: I didn't experience any of this in the actual Postman application.
While the server waits for chrome to send a request, it cannot service any other requests. To prevent this from happening, consider using an asynchronous approach.

UDP relay implementation do not work as I expected

I am trying to implement the relay of UDP communication.
For example, I have two terminals:
192.168.10.5
192.168.10.6
I would like to monitor between the two by way of 192.168.10.3.
My environment:
Unity 5.1.2-f1 on MacOS X 10.8.5 using C#
Following is my code snippet related to the UDP communication.
void Monitor() {
UdpClient client = new UdpClient (port);
client.Client.ReceiveTimeout = 1000; // msec
client.Client.Blocking = false;
while (ToggleComm.isOn) {
try {
IPEndPoint anyIP = new IPEndPoint(IPAddress.Any, 0);
byte[] data = client.Receive(ref anyIP);
string text = Encoding.ASCII.GetString(data);
if (text.Length == 0) {
Thread.Sleep(20);
continue;
}
string fromIP = anyIP.Address.ToString();
// send to the other
if (fromIP.Equals(ipadr1)) {
client.Send(data, data.Length, ipadr2, port);
Debug.Log("from: " + ipadr1 + " to " + ipadr2 + data);
} else {
client.Send(data, data.Length, ipadr1, port);
Debug.Log("from: " + ipadr2 + " to " + ipadr1 + data);
}
}
catch (Exception err) {
}
// without this sleep, on android, the app will freeze at Unity splash screen
Thread.Sleep(200);
}
client.Close ();
}
With the code above,
I can send from 192.168.10.5 to 192.168.10.3
I can send from 192.168.10.3 to 192.168.10.6 (relay)
I can receive at 192.168.10.3 from 192.168.10.6
I cannot receive at 192.168.10.5 from 192.168.10.3
where 192.168.10.6 works as echo server, returning received string back.
My debug print on the relay says
from: 192.168.10.5 to 192.168.10.6
from: 192.168.10.6 to 192.168.10.5
It seems that the relay (192.168.10.3) send to 192.168.10.5, but 192.168.10.5 cannot receive the relayed one.

Following code worked (not elegant yet, though).
I had misunderstanding about port of the sender and receiver.
void Monitor() {
UdpClient client = new UdpClient (port);
client.Client.ReceiveTimeout = 300; // msec
client.Client.Blocking = false;
string fromPort = "6000"; // at first 6000 is set as dummy
while (ToggleComm.isOn) {
try {
IPEndPoint anyIP = new IPEndPoint(IPAddress.Any, 0);
byte[] data = client.Receive(ref anyIP);
string text = Encoding.ASCII.GetString(data);
if (text.Length == 0) {
Thread.Sleep(20);
continue;
}
string fromIP = anyIP.Address.ToString();
// send to the other
if (fromIP.Equals(ipadr1)) {
fromPort = anyIP.Port.ToString(); // store the port
client.Send(data, data.Length, ipadr2, port);
Debug.Log("1 from: " + fromIP + "(" + fromPort
+ ") to " + ipadr2 + "(" + port.ToString() + ")");
} else {
client.Send(data, data.Length, ipadr1, Convert.ToInt32(fromPort));
Debug.Log("2 from: " + fromIP + "(" + "..."
+ ") to " + ipadr1 + "(" + fromPort + ")");
}
}
catch (Exception err) {
}
// without this sleep, on android, the app will freeze at Unity splash screen
Thread.Sleep(200);
}
client.Close ();
}
I put the unity project at github (v0.3)

Websockets - disconnects on server message

I'm new to Websockets and looking for working samples using WS and c# console application.
I ran into this one, but i already have a problem. It seems that connection is closed when server sends a message to client. I'm not sure but i think handshake is ok. Here is a code:
Server:
using System;
using System.Net.Sockets;
using System.Net;
using System.Security.Cryptography;
using System.Threading;
namespace ConsoleApplication1
{
class Program
{
static Socket serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP);
static private string guid = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
static void Main(string[] args)
{
serverSocket.Bind(new IPEndPoint(IPAddress.Any, 8080));
serverSocket.Listen(128);
serverSocket.BeginAccept(null, 0, OnAccept, null);
Console.Read();
}
private static void OnAccept(IAsyncResult result)
{
byte[] buffer = new byte[1024];
try
{
Socket client = null;
string headerResponse = "";
if (serverSocket != null && serverSocket.IsBound)
{
client = serverSocket.EndAccept(result);
var i = client.Receive(buffer);
headerResponse = (System.Text.Encoding.UTF8.GetString(buffer)).Substring(0, i);
// write received data to the console
Console.WriteLine(headerResponse);
Console.WriteLine("=====================");
}
if (client != null)
{
/* Handshaking and managing ClientSocket */
var key = headerResponse.Replace("ey:", "`")
.Split('`')[1] // dGhlIHNhbXBsZSBub25jZQ== \r\n .......
.Replace("\r", "").Split('\n')[0] // dGhlIHNhbXBsZSBub25jZQ==
.Trim();
// key should now equal dGhlIHNhbXBsZSBub25jZQ==
var test1 = AcceptKey(ref key);
var newLine = "\r\n";
var response = "HTTP/1.1 101 Switching Protocols" + newLine
+ "Upgrade: websocket" + newLine
+ "Connection: Upgrade" + newLine
+ "Sec-WebSocket-Accept: " + test1 + newLine + newLine
//+ "Sec-WebSocket-Protocol: chat, superchat" + newLine
//+ "Sec-WebSocket-Version: 13" + newLine
;
// which one should I use? none of them fires the onopen method
client.Send(System.Text.Encoding.UTF8.GetBytes(response));
var i = client.Receive(buffer); // wait for client to send a message
// once the message is received decode it in different formats
Console.WriteLine(Convert.ToBase64String(buffer).Substring(0, i));
Console.WriteLine("=====================");
Console.WriteLine("\n\nPress enter to send data to client");
Console.Read();
var subA = SubArray<byte>(buffer, 0, i);
client.Send(subA);
Console.Read();
Thread.Sleep(10000);//wait for message to be send
}
}
catch (SocketException exception)
{
throw exception;
}
finally
{
if (serverSocket != null && serverSocket.IsBound)
{
serverSocket.BeginAccept(null, 0, OnAccept, null);
}
}
}
public static T[] SubArray<T>(T[] data, int index, int length)
{
T[] result = new T[length];
Array.Copy(data, index, result, 0, length);
return result;
}
private static string AcceptKey(ref string key)
{
string longKey = key + guid;
byte[] hashBytes = ComputeHash(longKey);
return Convert.ToBase64String(hashBytes);
}
static SHA1 sha1 = SHA1CryptoServiceProvider.Create();
private static byte[] ComputeHash(string str)
{
return sha1.ComputeHash(System.Text.Encoding.ASCII.GetBytes(str));
}
}
}
Clent:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<script type="text/javascript">
function connect() {
var ws = new WebSocket("ws://localhost:8080/service");
ws.onopen = function () {
alert("About to send data");
ws.send("Hello World"); // I WANT TO SEND THIS MESSAGE TO THE SERVER!!!!!!!!
alert("Message sent!");
};
ws.onmessage = function (evt) {
alert("About to receive data");
var received_msg = evt.data;
alert("Message received = "+received_msg);
};
ws.onclose = function () {
// websocket is closed.
alert("Connection is closed...");
};
};
</script>
</head>
<body style="font-size:xx-large" >
<div>
Click here to start</div>
</body>
</html>
Here is a connection request and message from client:
Any help will be appreciated.

You cannot just "echo" the buffer you received. The RFC says, that frames from client to server must be masked. It doesn't say that messages from server to client must not, but at least for Chrome it shouldn't.
Hence, if you want to echo data, you have to decode (unmask) the frame and construct a new one. The payload needs to be XOR'ed byte-by-byte with the mask key.
Or simply send data like this:
byte[] send = new byte[3 + 2];
send[0] = 0x81; // last frame, text
send[1] = 3; // not masked, length 3
send[2] = 0x41;
send[3] = 0x42;
send[4] = 0x43;
nwStream.Write(send, 0, send.Length); // nwStream = client.GetStream(), client is a TcpClient

JeffRSon is correct. But it should be noted that section 5.1 of RFC 6455 does mention;
... A server MUST NOT mask any frames that it sends to the client. A client MUST close a connection if it detects a masked frame. ...

Creating a "Hello World" WebSocket example

I don't understand why I cannot make the following code work. I want to connect with JavaScript to my server console application. And then send data to the server.
Here is the server code:
static void Main(string[] args)
{
TcpListener server = new TcpListener(IPAddress.Parse("127.0.0.1"), 9998);
server.Start();
var client = server.AcceptTcpClient();
var stream = client.GetStream();
while (true)
{
var buffer = new byte[1024];
// wait for data to be received
var bytesRead = stream.Read(buffer, 0, buffer.Length);
var r = System.Text.Encoding.UTF8.GetString(buffer);
// write received data to the console
Console.WriteLine(r.Substring(0, bytesRead));
}
}
and here is the JavaScript:
var ws = new WebSocket("ws://localhost:9998/service");
ws.onopen = function () {
ws.send("Hello World"); // I WANT TO SEND THIS MESSAGE TO THE SERVER!!!!!!!!
};
ws.onmessage = function (evt) {
var received_msg = evt.data;
alert("Message is received...");
};
ws.onclose = function () {
// websocket is closed.
alert("Connection is closed...");
};
When I run that code this is what happens:
Note that when I run the JavaScript the server accepts and successfully establishes a connection. JavaScript is not able to send data though. Whenever I place the send method it will not send even though a connection is established. How can I make this work?

WebSockets is protocol that relies on TCP streamed connection. Although WebSockets is Message based protocol.
If you want to implement your own protocol then I recommend to use latest and stable specification (for 18/04/12) RFC 6455.
This specification contains all necessary information regarding handshake and framing. As well most of description on scenarios of behaving from browser side as well as from server side.
It is highly recommended to follow what recommendations tells regarding server side during implementing of your code.
In few words, I would describe working with WebSockets like this:
Create server Socket (System.Net.Sockets) bind it to specific port, and keep listening with asynchronous accepting of connections. Something like that:
Socket serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP);
serverSocket.Bind(new IPEndPoint(IPAddress.Any, 8080));
serverSocket.Listen(128);
serverSocket.BeginAccept(null, 0, OnAccept, null);
You should have accepting function "OnAccept" that will implement handshake. In future it has to be in another thread if system is meant to handle huge amount of connections per second.
private void OnAccept(IAsyncResult result) {
try {
Socket client = null;
if (serverSocket != null && serverSocket.IsBound) {
client = serverSocket.EndAccept(result);
}
if (client != null) {
/* Handshaking and managing ClientSocket */
}
} catch(SocketException exception) {
} finally {
if (serverSocket != null && serverSocket.IsBound) {
serverSocket.BeginAccept(null, 0, OnAccept, null);
}
}
}
After connection established, you have to do handshake. Based on specification 1.3 Opening Handshake, after connection established you will receive basic HTTP request with some information. Example:
GET /chat HTTP/1.1
Host: server.example.com
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
Origin: http://example.com
Sec-WebSocket-Protocol: chat, superchat
Sec-WebSocket-Version: 13
This example is based on version of protocol 13. Bear in mind that older versions have some differences but mostly latest versions are cross-compatible. Different browsers may send you some additional data. For example Browser and OS details, cache and others.
Based on provided handshake details, you have to generate answer lines, they are mostly same, but will contain Accept-Key, that is based on provided Sec-WebSocket-Key. In specification 1.3 it is described clearly how to generate response key.
Here is my function I've been using for V13:
static private string guid = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
private string AcceptKey(ref string key) {
string longKey = key + guid;
SHA1 sha1 = SHA1CryptoServiceProvider.Create();
byte[] hashBytes = sha1.ComputeHash(System.Text.Encoding.ASCII.GetBytes(longKey));
return Convert.ToBase64String(hashBytes);
}
Handshake answer looks like that:
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
But accept key have to be the generated one based on provided key from client and method AcceptKey I provided before. As well, make sure after last character of accept key you put two new lines "\r\n\r\n".
After handshake answer is sent from server, client should trigger "onopen" function, that means you can send messages after.
Messages are not sent in raw format, but they have Data Framing. And from client to server as well implement masking for data based on provided 4 bytes in message header. Although from server to client you don't need to apply masking over data. Read section 5. Data Framing in specification.
Here is copy-paste from my own implementation. It is not ready-to-use code, and have to be modified, I am posting it just to give an idea and overall logic of read/write with WebSocket framing. Go to this link.
After framing is implemented, make sure that you receive data right way using sockets. For example to prevent that some messages get merged into one, because TCP is still stream based protocol. That means you have to read ONLY specific amount of bytes. Length of message is always based on header and provided data length details in header it self. So when you receiving data from Socket, first receive 2 bytes, get details from header based on Framing specification, then if mask provided another 4 bytes, and then length that might be 1, 4 or 8 bytes based on length of data. And after data it self. After you read it, apply demasking and your message data is ready to use.
You might want to use some Data Protocol, I recommend to use JSON due traffic economy and easy to use on client side in JavaScript. For server side you might want to check some of parsers. There is lots of them, google can be really helpful.
Implementing own WebSockets protocol definitely have some benefits and great experience you get as well as control over protocol it self. But you have to spend some time doing it, and make sure that implementation is highly reliable.
In same time you might have a look in ready to use solutions that google (again) have enough.

(Posted answer on behalf of the OP).
I am able to send data now. This is my new version of the program thanks to your answers and the code of #Maksims Mihejevs.
Server
using System;
using System.Net.Sockets;
using System.Net;
using System.Security.Cryptography;
using System.Threading;
namespace ConsoleApplication1
{
class Program
{
static Socket serverSocket = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.IP);
static private string guid = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
static void Main(string[] args)
{
serverSocket.Bind(new IPEndPoint(IPAddress.Any, 8080));
serverSocket.Listen(128);
serverSocket.BeginAccept(null, 0, OnAccept, null);
Console.Read();
}
private static void OnAccept(IAsyncResult result)
{
byte[] buffer = new byte[1024];
try
{
Socket client = null;
string headerResponse = "";
if (serverSocket != null && serverSocket.IsBound)
{
client = serverSocket.EndAccept(result);
var i = client.Receive(buffer);
headerResponse = (System.Text.Encoding.UTF8.GetString(buffer)).Substring(0,i);
// write received data to the console
Console.WriteLine(headerResponse);
}
if (client != null)
{
/* Handshaking and managing ClientSocket */
var key = headerResponse.Replace("ey:", "`")
.Split('`')[1] // dGhlIHNhbXBsZSBub25jZQ== \r\n .......
.Replace("\r", "").Split('\n')[0] // dGhlIHNhbXBsZSBub25jZQ==
.Trim();
// key should now equal dGhlIHNhbXBsZSBub25jZQ==
var test1 = AcceptKey(ref key);
var newLine = "\r\n";
var response = "HTTP/1.1 101 Switching Protocols" + newLine
+ "Upgrade: websocket" + newLine
+ "Connection: Upgrade" + newLine
+ "Sec-WebSocket-Accept: " + test1 + newLine + newLine
//+ "Sec-WebSocket-Protocol: chat, superchat" + newLine
//+ "Sec-WebSocket-Version: 13" + newLine
;
// which one should I use? none of them fires the onopen method
client.Send(System.Text.Encoding.UTF8.GetBytes(response));
var i = client.Receive(buffer); // wait for client to send a message
// once the message is received decode it in different formats
Console.WriteLine(Convert.ToBase64String(buffer).Substring(0, i));
Console.WriteLine("\n\nPress enter to send data to client");
Console.Read();
var subA = SubArray<byte>(buffer, 0, i);
client.Send(subA);
Thread.Sleep(10000);//wait for message to be send
}
}
catch (SocketException exception)
{
throw exception;
}
finally
{
if (serverSocket != null && serverSocket.IsBound)
{
serverSocket.BeginAccept(null, 0, OnAccept, null);
}
}
}
public static T[] SubArray<T>(T[] data, int index, int length)
{
T[] result = new T[length];
Array.Copy(data, index, result, 0, length);
return result;
}
private static string AcceptKey(ref string key)
{
string longKey = key + guid;
byte[] hashBytes = ComputeHash(longKey);
return Convert.ToBase64String(hashBytes);
}
static SHA1 sha1 = SHA1CryptoServiceProvider.Create();
private static byte[] ComputeHash(string str)
{
return sha1.ComputeHash(System.Text.Encoding.ASCII.GetBytes(str));
}
}
}
JavaScript:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<script type="text/javascript">
function connect() {
var ws = new WebSocket("ws://localhost:8080/service");
ws.onopen = function () {
alert("About to send data");
ws.send("Hello World"); // I WANT TO SEND THIS MESSAGE TO THE SERVER!!!!!!!!
alert("Message sent!");
};
ws.onmessage = function (evt) {
alert("About to receive data");
var received_msg = evt.data;
alert("Message received = "+received_msg);
};
ws.onclose = function () {
// websocket is closed.
alert("Connection is closed...");
};
};
</script>
</head>
<body style="font-size:xx-large" >
<div>
Click here to start</div>
</body>
</html>
When I run that code I am able to send and receive data from both the client and the server. The only problem is that the messages are encrypted when they arrive to the server. Here are the steps of how the program runs:
Note how the message from the client is encrypted.

I couldnt find a simple working example anywhere (as of Jan 19), so here is an updated version. I have chrome version 71.0.3578.98.
C# Websocket server :
using System;
using System.Text;
using System.Net;
using System.Net.Sockets;
using System.Security.Cryptography;
namespace WebSocketServer
{
class Program
{
static Socket serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP);
static private string guid = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
static void Main(string[] args)
{
serverSocket.Bind(new IPEndPoint(IPAddress.Any, 8080));
serverSocket.Listen(1); //just one socket
serverSocket.BeginAccept(null, 0, OnAccept, null);
Console.Read();
}
private static void OnAccept(IAsyncResult result)
{
byte[] buffer = new byte[1024];
try
{
Socket client = null;
string headerResponse = "";
if (serverSocket != null && serverSocket.IsBound)
{
client = serverSocket.EndAccept(result);
var i = client.Receive(buffer);
headerResponse = (System.Text.Encoding.UTF8.GetString(buffer)).Substring(0, i);
// write received data to the console
Console.WriteLine(headerResponse);
Console.WriteLine("=====================");
}
if (client != null)
{
/* Handshaking and managing ClientSocket */
var key = headerResponse.Replace("ey:", "`")
.Split('`')[1] // dGhlIHNhbXBsZSBub25jZQ== \r\n .......
.Replace("\r", "").Split('\n')[0] // dGhlIHNhbXBsZSBub25jZQ==
.Trim();
// key should now equal dGhlIHNhbXBsZSBub25jZQ==
var test1 = AcceptKey(ref key);
var newLine = "\r\n";
var response = "HTTP/1.1 101 Switching Protocols" + newLine
+ "Upgrade: websocket" + newLine
+ "Connection: Upgrade" + newLine
+ "Sec-WebSocket-Accept: " + test1 + newLine + newLine
//+ "Sec-WebSocket-Protocol: chat, superchat" + newLine
//+ "Sec-WebSocket-Version: 13" + newLine
;
client.Send(System.Text.Encoding.UTF8.GetBytes(response));
var i = client.Receive(buffer); // wait for client to send a message
string browserSent = GetDecodedData(buffer, i);
Console.WriteLine("BrowserSent: " + browserSent);
Console.WriteLine("=====================");
//now send message to client
client.Send(GetFrameFromString("This is message from server to client."));
System.Threading.Thread.Sleep(10000);//wait for message to be sent
}
}
catch (SocketException exception)
{
throw exception;
}
finally
{
if (serverSocket != null && serverSocket.IsBound)
{
serverSocket.BeginAccept(null, 0, OnAccept, null);
}
}
}
public static T[] SubArray<T>(T[] data, int index, int length)
{
T[] result = new T[length];
Array.Copy(data, index, result, 0, length);
return result;
}
private static string AcceptKey(ref string key)
{
string longKey = key + guid;
byte[] hashBytes = ComputeHash(longKey);
return Convert.ToBase64String(hashBytes);
}
static SHA1 sha1 = SHA1CryptoServiceProvider.Create();
private static byte[] ComputeHash(string str)
{
return sha1.ComputeHash(System.Text.Encoding.ASCII.GetBytes(str));
}
//Needed to decode frame
public static string GetDecodedData(byte[] buffer, int length)
{
byte b = buffer[1];
int dataLength = 0;
int totalLength = 0;
int keyIndex = 0;
if (b - 128 <= 125)
{
dataLength = b - 128;
keyIndex = 2;
totalLength = dataLength + 6;
}
if (b - 128 == 126)
{
dataLength = BitConverter.ToInt16(new byte[] { buffer[3], buffer[2] }, 0);
keyIndex = 4;
totalLength = dataLength + 8;
}
if (b - 128 == 127)
{
dataLength = (int)BitConverter.ToInt64(new byte[] { buffer[9], buffer[8], buffer[7], buffer[6], buffer[5], buffer[4], buffer[3], buffer[2] }, 0);
keyIndex = 10;
totalLength = dataLength + 14;
}
if (totalLength > length)
throw new Exception("The buffer length is small than the data length");
byte[] key = new byte[] { buffer[keyIndex], buffer[keyIndex + 1], buffer[keyIndex + 2], buffer[keyIndex + 3] };
int dataIndex = keyIndex + 4;
int count = 0;
for (int i = dataIndex; i < totalLength; i++)
{
buffer[i] = (byte)(buffer[i] ^ key[count % 4]);
count++;
}
return Encoding.ASCII.GetString(buffer, dataIndex, dataLength);
}
//function to create frames to send to client
/// <summary>
/// Enum for opcode types
/// </summary>
public enum EOpcodeType
{
/* Denotes a continuation code */
Fragment = 0,
/* Denotes a text code */
Text = 1,
/* Denotes a binary code */
Binary = 2,
/* Denotes a closed connection */
ClosedConnection = 8,
/* Denotes a ping*/
Ping = 9,
/* Denotes a pong */
Pong = 10
}
/// <summary>Gets an encoded websocket frame to send to a client from a string</summary>
/// <param name="Message">The message to encode into the frame</param>
/// <param name="Opcode">The opcode of the frame</param>
/// <returns>Byte array in form of a websocket frame</returns>
public static byte[] GetFrameFromString(string Message, EOpcodeType Opcode = EOpcodeType.Text)
{
byte[] response;
byte[] bytesRaw = Encoding.Default.GetBytes(Message);
byte[] frame = new byte[10];
long indexStartRawData = -1;
long length = (long)bytesRaw.Length;
frame[0] = (byte)(128 + (int)Opcode);
if (length <= 125)
{
frame[1] = (byte)length;
indexStartRawData = 2;
}
else if (length >= 126 && length <= 65535)
{
frame[1] = (byte)126;
frame[2] = (byte)((length >> 8) & 255);
frame[3] = (byte)(length & 255);
indexStartRawData = 4;
}
else
{
frame[1] = (byte)127;
frame[2] = (byte)((length >> 56) & 255);
frame[3] = (byte)((length >> 48) & 255);
frame[4] = (byte)((length >> 40) & 255);
frame[5] = (byte)((length >> 32) & 255);
frame[6] = (byte)((length >> 24) & 255);
frame[7] = (byte)((length >> 16) & 255);
frame[8] = (byte)((length >> 8) & 255);
frame[9] = (byte)(length & 255);
indexStartRawData = 10;
}
response = new byte[indexStartRawData + length];
long i, reponseIdx = 0;
//Add the frame bytes to the reponse
for (i = 0; i < indexStartRawData; i++)
{
response[reponseIdx] = frame[i];
reponseIdx++;
}
//Add the data bytes to the response
for (i = 0; i < length; i++)
{
response[reponseIdx] = bytesRaw[i];
reponseIdx++;
}
return response;
}
}
}
Client html and javascript:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<script type="text/javascript">
var socket = new WebSocket('ws://localhost:8080/websession');
socket.onopen = function() {
// alert('handshake successfully established. May send data now...');
socket.send("Hi there from browser.");
};
socket.onmessage = function (evt) {
//alert("About to receive data");
var received_msg = evt.data;
alert("Message received = "+received_msg);
};
socket.onclose = function() {
alert('connection closed');
};
</script>
</head>
<body>
</body>
</html>

WebSockets are implemented with a protocol that involves handshake between client and server. I don't imagine they work very much like normal sockets. Read up on the protocol, and get your application to talk it. Alternatively, use an existing WebSocket library, or .Net4.5beta which has a WebSocket API.

Issue
Since you are using WebSocket, spender is correct. After recieving the initial data from the WebSocket, you need to send the handshake message from the C# server before any further information can flow.
HTTP/1.1 101 Web Socket Protocol Handshake
Upgrade: websocket
Connection: Upgrade
WebSocket-Origin: example
WebSocket-Location: something.here
WebSocket-Protocol: 13
Something along those lines.
You can do some more research into how WebSocket works on w3 or google.
Links and Resources
Here is a protocol specifcation: https://datatracker.ietf.org/doc/html/draft-hixie-thewebsocketprotocol-76#section-1.3
List of working examples:
https://stackoverflow.com/a/5866975/184746
https://stackoverflow.com/a/2212752/184746
http://ashishware.com/websocksample.shtml
http://www.sencha.com/forum/showthread.php?99842-WebSocket-server-in-C

C# Async Webserver - how to send data to client

This might be a piece of cake for any experienced C# developer
What you see here is a sample Asynchronous webserver
using System;
using System.Text;
using System.Net;
using System.Net.Sockets;
using System.Threading;
namespace SimpleServer
{
class Program
{
public static void ReceiveCallback(IAsyncResult AsyncCall)
{
System.Text.ASCIIEncoding encoding = new System.Text.ASCIIEncoding();
Byte[] message = encoding.GetBytes("I am a little busy, come back later!");
Socket listener = (Socket)AsyncCall.AsyncState;
Socket client = listener.EndAccept(AsyncCall);
Console.WriteLine("Received Connection from {0}", client.RemoteEndPoint);
client.Send(message);
Console.WriteLine("Ending the connection");
client.Close();
listener.BeginAccept(new AsyncCallback(ReceiveCallback), listener);
}
public static void Main()
{
try
{
IPAddress localAddress = IPAddress.Parse("127.0.0.1");
Socket listenSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
IPEndPoint ipEndpoint = new IPEndPoint(localAddress, 8080);
listenSocket.Bind(ipEndpoint);
listenSocket.Listen(1);
listenSocket.BeginAccept(new AsyncCallback(ReceiveCallback), listenSocket);
while (true)
{
Console.WriteLine("Busy Waiting....");
Thread.Sleep(2000);
}
}
catch (Exception e)
{
Console.WriteLine("Caught Exception: {0}", e.ToString());
}
}
}
I downloaded this from the web, in order to have a basic model to work on.
Basically what I need to do is run this webserver as a process in a computer. It will be listening to por 8080 all the time, and when a client computer sends a request, this server will process some data and send back a result as a string.
I created a small project with this code (which is functional as is), but when it executes the line
client.Send(message);
all I get is an error in the browser, or at most a blank page
I suspect I need to define the HTTP headers to send with the (message), but I have been searching the web on this with no luck
Anyone willing to help?
Thanks!

You need something like this
HTTP/1.1 200 OK
Server: My Little Server
Content-Length: [Size of the Message here]
Content-Language: en
Content-Type: text/html
Connection: close
[Message]
If you send this hole block of data it should work correctly.
Edit:
You can use this Method:
public static void SendHeader(string sMIMEHeader, int iTotBytes, string sStatusCode, ref Socket mySocket)
{
String sBuffer = "";
// if Mime type is not provided set default to text/html
if (sMIMEHeader.Length == 0)
{
sMIMEHeader = "text/html"; // Default Mime Type is text/html
}
sBuffer = sBuffer + "HTTP/1.1" + sStatusCode + "\r\n";
sBuffer = sBuffer + "Server: cx1193719-b\r\n";
sBuffer = sBuffer + "Content-Type: " + sMIMEHeader + "\r\n";
sBuffer = sBuffer + "Accept-Ranges: bytes\r\n";
sBuffer = sBuffer + "Content-Length: " + iTotBytes + "\r\n\r\n";
Byte[] bSendData = Encoding.ASCII.GetBytes(sBuffer);
mySocket.Send(Encoding.ASCII.GetBytes(sBuffer),Encoding.ASCII.GetBytes(sBuffer).Length, 0);
Console.WriteLine("Total Bytes : " + iTotBytes.ToString());
}
And in your Main()-Method you should replace
Byte[] message = encoding.GetBytes("I am a little busy, come back later!");
with
string messageString = "I am a little busy, come back later!";
Byte[] message = encoding.GetBytes(messageString);
and then insert
// Unicode char may have size more than 1 byte so we should use message.Length instead of messageString.Length
SendHeader("text/html", message.Length, "202 OK", ref client);
before
client.Send(message);
That's all.