Library tutorials & articles
Socket Programming in C# - Part 1
- Introduction
- System.Net.Sockets namespace
- Making a Connection and Sending Data
- Using the Sample Program
Making a Connection and Sending Data
With this info lets now try to check the code behind this:
Socket programming in .NET is made possible by the Socket class present inside the System.Net.Sockets namespace. This Socket class has several method and properties and a constructor. The first step is to create an object of this class. Since there is only one constructor we have no choice but to use it.
Here is how to create the socket:
m_socListener = new Socket(AddressFamily.InterNetwork,SocketType.Stream,ProtocolType.Tcp);
The first parameter is the address family which we will use, in this case,
interNetwork (which is IP version 4) - other options include Banyan
NetBios, AppleTalk etc. (AddressFamily is an enum defined in Sockets
namespace). Next we need to specify socket type: and we would use reliable
two way connection-based sockets (stream) instead of un-reliable Connectionless
sockets (datagrams)
. So we obviously specify stream as the socket type and finally we are using
TCP/IP so we would specify protocol type as Tcp.
Once we have created a Socket we need to make a connection to the server
since we are using connection-based communication.
To connect to the remote computer we need to know the IP Address and port
at which to connect.
In .NET there is a class under System.Net namespace called IPEndPoint which
represents a network computer as an IP address and a port number.
The IPEndPoint has two constructors - one that takes a IP Address and Port
number and one that takes long and port number. Since we have computer
IP address we would use the former
public IPEndPoint(System.Net.IPAddress address, int port);
As you can see the first parameter takes a IPAddress object. If you examine
the IPAddress class you will see that it has a static method called Parse that
returns IPAddress given a string (of dot notation) and second
parameter will be the port number. Once we have endpoint ready we can use Connect method
of this Socket class to connect to the end point ( remote server computer ).
Here is the code:
System.Net.IPAddress ipAdd = System.Net.IPAddress.Parse("10.10.101.200");
System.Net.IPEndPoint remoteEP = new IPEndPoint (iAdd,8221);
m_socClient.Connect (remoteEP);
These three lines of code will make a connection to the remote host running on computer with IP 10.10.101.200 and listening at port 8221. If the Server is running and started ( listening ), the connection will succeed. If however the server is not running an exception called SocketException will be thrown. If you catch the exception and check the Message property of the exception in this case you see following text:
"No connection could be made because the target machine
actively refused it."
Similarly if you already have made a connection and the server somehow dies , you will get following exception if you try to send data.
"An existing connection was forcibly closed by the
remote host"
Assuming that the connection is made, you can send data to other side using the Send method of the Socket class. Send method has several overloads. All of them take a byte array . For example if you want to send "Hello There" to host you can use following call:
try
{
String szData = "Hello There";
byte[] byData = System.Text.Encoding.ASCII.GetBytes(szData);
m_socClient.Send(byData);
}
catch (SocketException se)
{
MessageBox.Show ( se.Message );
}
Note that the Send method is blocking. This means the call will block (wait)
till the data has been sent or an exception has been thrown. There is an non-blocking
version of the send which we will discuss in the next part
of
this article. Similar to Send there is a Receive method on the Socket class. You can receive
data using following call:
byte [] buffer = new byte[1024];
int iRx = m_socClient.Receive (buffer);
The Receive method again is blocking. It means that if there is no data available
the call will block until some data arrives or an exception is thrown.
Non-blocking version of Receive method is more useful than the non-blocking
version of Send because if we opt for block Receive , we are effectively doing
polling. There is no events about data arrival. This model does not work well
for serious applications. But all that is the subject of our next part of this
article. For now we will settle with the blocking version.
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hello I want to send an object with tcp socket ( a class that i made it). I see here that you r sending string (converted to byte array)
How can i convert a class to byte array so i can send it with this socket???? (the winsock object in C# it takes an "object" parameter and it send it ,this socket can not take anything else except the byte array)
If u encounter a Cross-Threading problem u may need to do a little fix. Replace OnDataReceived function in the server side with that code:
This tutorial provides just basic network programming knowledge, in order to build high performance client - server solution you need more than that.
Clean and scalable server architecture should be designed. Not easy task at all
I would suggest to take a look at XF.Server component for server solutions written in .NET / C# / VB.NET
The only thing that should be added is the server's business logic. I've tried the component, it has nice design and interesting solutions to get maximum performance.
Hi,
I want to develop an application in C# which is connecting to UNIX server throgh socket and execute Unix commands from c# application. Please send me any sample programe in C# which uses socket programming to connect to unix server and execute unix command.
thanks,
Mak
I want an application , where a single client using more than one server (Same Application running in more than one machines.).Client listening to a single port for all the servers it connected to.
Client application will receive huge data frequently. Server will process and send the data to client.
As i want the application to be started first i made the main application as Server. Am i right.
or Do we have option for passive Servers.
With Thanks,
Eswar
After the client is connected, the server recieves only 1 byte of data.
If I introduce a delay(Thread.Sleep, MBox, or a breakpoint), between the OnClientConnect, WaitForData and OnDataReceived functions, I get complete data.
This shouldn't happen logically. I'm wondering what might be the problem.
Sir i am new to .Net and i want to create chatting software which can communicate over the internet too.
I have searched a lot but the help which i found couldn't solve my problem. Please sir
i have to complete my semester project of Bs(Computer Engineering) i need help.
you can mail me the solution on my email dr_hunaindurrani@yahoo.com i will be great full to you.
Thanks in advance
Hunain Durrani.
Ok, here is the fix to make the samples work under C# 2005 without exceptions.
In the SocketServer project modify the SocketServer class as follows:
1. Add the following delegate declaration:
// This delegate enables asynchronous calls for setting
// the text property on a TextBox control.
delegate void AppendTextCallback(string text);
2. Add the following method:
// If the calling thread is different from the thread that
// created the TextBox control, this method creates a
// AppendTextCallback and calls itself asynchronously using the
// Invoke method.
//
// If the calling thread is the same as the thread that created
// the TextBox control, the Text property is set directly.
private void AppendRxText(string text)
{
// InvokeRequired required compares the thread ID of the
// calling thread to the thread ID of the creating thread.
// If these threads are different, it returns true.
if (this.txtDataRx.InvokeRequired)
{
AppendTextCallback d = new AppendTextCallback(AppendRxText);
this.Invoke(d, new object[] { text });
}
else
{
txtDataRx.Text = txtDataRx.Text + text;
}
}
3. Replace the OnDataReceived method with the following, or make the minor one line code change
as commented in the method below if you prefer:
public void OnDataReceived(IAsyncResult asyn)
{
try
{
CSocketPacket theSockId = (CSocketPacket)asyn.AsyncState ;
//end receive...
int iRx = 0 ;
iRx = theSockId.thisSocket.EndReceive (asyn);
char[] chars = new char[iRx + 1];
System.Text.Decoder d = System.Text.Encoding.UTF8.GetDecoder();
int charLen = d.GetChars(theSockId.dataBuffer, 0, iRx, chars, 0);
System.String szData = new System.String(chars);
// Old offending line
//txtDataRx.Text = txtDataRx.Text + szData;
AppendRxText(szData);
WaitForData(m_socWorker );
}
catch (ObjectDisposedException )
{
System.Diagnostics.Debugger.Log(0,"1","\nOnDataReceived: Socket has been closed\n");
}
catch(SocketException se)
{
MessageBox.Show (se.Message );
}
}
I am using Visual C# 2005. It turns out that there are some cross thread calls to forms controls which are flagged as unsafe when running under C# 2005. I will post fixes to these a little later.
there is aproblem meet me ,i designed aprogram simulate the work of credit card by designing two programs one used by auser and the other one for the administration and deal with database ,but when i put the two program on different computer they are not work
the tcplistner statement as follow:
listener = new TcpListener(1500);
the tcpclient statement as follow:
client = new TcpClient("192.168.1.1", 1500);
since the "192.168.1.1" is the ip address of the machine that the server program run at
How can we reduce this timeout?
What is the method to control it?
Thanks
assalam-o-aleykum, im raheel from pakistan, and i want to know about client to client messanger, plz guide me. thanks. my mail raheel_s81@hotmail.com
Hi
I am trying server request/response program using socket class. here i couldn't send headers with the request to the proxy server.when i send the request i should able to get the response from the server.
if u have any idea please help me out.
Regards
request.
Regarding blocking socket calls. Are u assuming .net does the polling. As no additional code has to be written for polling. So no need to return to main thread and a delegate also is not required.
Now consider in asynchronous mode, multiple clients are connected. Then the delegates for beginreceive will fire at will and when multiple fire at same time, it gets stacked as there only one thread. Then the last delegate to be fired will be processed and then down the stack. In fact if we need to sequence something, a lot of coding is involved. The flow also is not clear and criss crosses.
Could you comment on the above. I have a req which needs sequential access of the messages and depends on a flow mapping of messages when there are multiple clients. I been thinking async(with delegates) will be an overhead and confusing/complicated to implement.
When the Client tries to connect to a disconnected IP address, there is a long timeout of 23 seconds...
How can we reduce this timeout?
What is the method to control it?
Thanks for help
you can do client / server in the same computer by useing concept "localhost" if you send to my your program i will correct to you and send to you .
and also i try to do multi client / server in c# programming if you can help my after .
I only speak a lite bit of english.
I would like to know how to run the server and the client in the
same computer to text my application before to start with two
diferents computers.
Thank Javier
This thread is for discussions of Socket Programming in C# - Part 1.