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Sockets and C#
As with everything, we must start somewhere, and that somewhere is here at
main()... If you look around the net...there's a ton of information on
sockets out there. And once you get past the basics of what a socket is
and why we need them, you'll soon realise that they aren't that bad. I'll
be showing you how to use the very basics of setting up sockets using C#...so
that you can receive or send some data to an IP address.
| Code: |
|
// files.cs
class
abc
{
static void
Main()
{
/* our program entry point*/
}
} |
But to make things interesting...we'll be connecting to a
server... a web server...google.com in this tutorial... Now when we
connect we'll get the html code and put it to a text file....we'll also put some
debug info to a text file, so we can see our code step by step.... so lets write
our text output code first:
| Code: |
|
class
debug
{
public static
void abc(string
str)
{
// FileMode - Append, Create,
CreateNew, Open, OpenOrCreate, or Truncate
// FileAccess - Read, ReadWrite, or
Write
// Read the whole file contents in
FileStream file = new
FileStream("abc.txt", FileMode.OpenOrCreate | FileMode.Append,
FileAccess.Write);
// Create a new stream to read from a
file
StreamWriter f = new
StreamWriter(file);
f.Write(str);
// Close StreamReader
f.Close();
// Close file
file.Close();
}//
End of abc(..)
}//
End of class abc |
So when we need to put data to our file...we can do this:
debug.abc("Starting Point A\r\n");
...code
debug.abc("Reached Point B\r\n");
Simple eh?... Well it will come in really useful as we go
step by step through our code :)
| Code: |
|
using
System.Net.Sockets;
//
Socket
using
System.Net;
// IPEndPoint
class
debug
[..]
// Blocking sockets entry point of program
class
Program
{
static void
Main()
{
debug.abc("Setting Up Socket:\r\n");
// +-- an
enum, which defines which networking we want to
// | use,
InterNetwork implies IP v 4
// |
//
| +- Socket type - reliable or
//
| | unreliable
//
| |
//
| | +- Protocol
//
| | |
Socket s = new
Socket(AddressFamily.InterNetwork,SocketType.Stream,ProtocolType.Tcp);
debug.abc("Socket s: " + s.ToString() + "\r\n");
}
} |
Setting Up Socket:
Socket s: System.Net.Sockets.Socket
Simple... but its not given us much yet... But its worth noting that C#
isn't like C or C++.... as we can't just check the return value of a Socket.
You'll find that if you can't open a socket, the application will throw an
exception error which you must catch and deal with.
| Code: |
|
class
Program
{
static void
Main()
{
// google.com -> 216.239.53.99:80
debug.abc("Setting Up Socket:\r\n");
// +-- an
enum, which defines which networking we want to
// | use,
InterNetwork implies IP v 4
// |
//
| +- Socket type - reliable or
//
| | unreliable
//
| |
//
| | +- Protocol
//
| | |
Socket s = new
Socket(AddressFamily.InterNetwork,SocketType.Stream,ProtocolType.Tcp);
// Connect to our server
debug.abc("Connecting to Server:\r\n");
int port = 80;
System.Net.IPAddress ipAdd = System.Net.IPAddress.Parse("216.239.53.99");
IPEndPoint cc = new IPEndPoint(
ipAdd, port );
s.Connect(cc);
if( !s.Connected )
debug.abc("unable to connect" );
}
} |
Or just in case you don't know the IP address, you can use the following
snippet :)
| Snippet: |
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IPHostEntry IPHost = Dns.Resolve("www.google.com");
IPAddress[] addr = IPHost.AddressList;
IPEndPoint cc = new IPEndPoint(
addr[0], port ); |
Lets send the command to the 'google' server for the html code... which is
'Get \r\n\r\n'... and in response the server will send the html text back.
| Code: |
|
class
Program
{
static void
Main()
{
// google.com -> 216.239.53.99:80
debug.abc("Setting Up Socket:\r\n");
// +-- an
enum, which defines which networking we want to
// | use,
InterNetwork implies IP v 4
// |
//
| +- Socket type - reliable or
//
| | unreliable
//
| |
//
| | +- Protocol
//
| | |
Socket s = new
Socket(AddressFamily.InterNetwork,SocketType.Stream,ProtocolType.Tcp);
// Connect to our server
debug.abc("Connecting to Server:\r\n");
int port = 80;
System.Net.IPAddress ipAdd = System.Net.IPAddress.Parse("216.239.53.99");
IPEndPoint cc = new IPEndPoint(
ipAdd, port );
s.Connect(cc);
// Send the request for the html
debug.abc("Sending:\r\n");
string szData = "GET /
HTTP/1.0\r\n\r\n";
byte[] byData =
System.Text.Encoding.ASCII.GetBytes(szData);
s.Send(byData, byData.Length, 0);
// Receiving the html from the server
debug.abc("Receive:\r\n");
byte [] buffer =
new byte[1024];
int iRx = s.Receive (buffer,
buffer.Length, 0);
string received =
System.Text.Encoding.ASCII.GetString(buffer, 0, iRx);
debug.abc(received);
s.Close();
}//
End of Main()
}//
End of class Program |
| txt file: |
Connecting to Server:
Sending:
Receive:
HTTP/1.0 200 OK
Connection: Keep-Alive
Date: Tue, 07 Oct 2003 12:55:03 GMT
Content-length: 2690
Server: GWS/2.1
Content-Type: text/html
Cache-control: private
Set-Cookie: PREF=ID=71fa3ae60e338d94:TM=1065531303:LM=1065531303:S=I4TjlpUJx6giMYjW;
expires=Sun, 17-Jan-2038 19:14:07 GMT; path=/; domain=.google.com
<html><head><meta http-equiv=".............(etc) |
One small problem with the code is that it receives the first 1000
bytes....and that could be a problem...what if where being sent a big html
file...possibly 12,000 bytes? Well we can do a small loop and keep
receiving the data until we've got it all:
| Code: |
| ...
// Receiving default html page
debug.abc("Receive:\r\n");
int iRxBytes = 1;
while( iRxBytes > 0 )
{
byte [] buffer =
new byte[1024];
iRxBytes = s.Receive (buffer, buffer.Length, 0);
string received =
System.Text.Encoding.ASCII.GetString(buffer, 0, iRxBytes);
debug.abc(received);
}// End while loop
s.Close();
... |
Okay our code does a simple socket setup....its up to you to experiment and
try other things....maybe write a small chat program :)
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