Net Sockets

Август 22, 2022

Содержание

2. References www.msdn.microsoft.com/library .Net Development/.Net Framework SDK/ .Net Framework/Reference/ClassLibrary/ System.Net.Sockets http://www.dotnetjunkies.com/quickstart/howto/doc/TCPUDP/DateTimeClient.aspx C# NetworkProgramming, Richard Blum, Sybex, 2003
3. What are Sockets? Sockets provide a common interface to the various protocols supported by networks. They
4. Socket Logical Structure
5. How do Sockets Function? There are several modes of operation available for sockets. A very common
6. Socket Client, Server, and Listener
7. Client/Server Configuration
8. Socket Data Transfer The receiving socket, either client or server, has a buffer that stores bytes
9. Non-Blocking Communication
10. Basic .Net Network Objects TCPListener TCPListener(port) AcceptTcpClient() AcceptSocket() Start() Stop() Socket Send(byte[], size, socketFlags) Receive(byte[], size,
11. More Network Programming Objects TCPClient TCPClient() Connect(IPAddress, port) GetStream() Close() NetworkStream NetworkStream(Socket) Read(byte[], offset, size) Write(byte[],
12. Simple Socket Client TcpClient tcpc = new TcpClient(); Byte[] read = new Byte[32]; // read buffer
13. Simple Socket Server TcpListener tcpl = new TcpListener(2048); // listen on port 2048 tcpl.Start(); while (true)
16. Multi-threaded Server If we want to support concurrent clients, the server must spawn a thread for
17. Define Thread’s Processing class threadProc { private Socket _sock = null; public threadProc(Socket sock) { _sock
18. Server Spawns Threads to Handle New Clients with threadProc.proc() // listen on port 2048 TcpListener tcpl
19. Clients now Wait for Server to Complete // Try to connect to the server tcpc.Connect(server, 2048);
20. Talk Protocol The hardest part of a client/server socket communication design is to control the active
21. Bilateral Channel Talk-Listen Protocol
22. Message Length Another vexing issue is that the receiver may not know how long a sent
23. Message Framing There are three solutions to this problem: Use fixed length messages – rarely useful
24. They’re Everywhere Virtually every network and internet communication method uses sockets, often in a way that
26. Скачать презентацию

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References
www.msdn.microsoft.com/library
.Net Development/.Net Framework SDK/
.Net Framework/Reference/ClassLibrary/
System.Net.Sockets
http://www.dotnetjunkies.com/quickstart/howto/doc/TCPUDP/DateTimeClient.aspx
C# NetworkProgramming, Richard Blum, Sybex, 2003
Win32 Sockets,

Jim Fawcett, Fall 2002

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What are Sockets?
Sockets provide a common interface to the various protocols

supported by networks.
They allow you to establish connections between machines to send and receive data.
Sockets support the simultaneous connection of multiple clients to a single server machine.

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Socket Logical Structure

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How do Sockets Function?
There are several modes of operation available for

sockets.
A very common mode is to establish a socket listener that listens on some port, say 4040, for connection requests.
When a socket client, from another process or a remote computer, requests a connection on port 4040, the listener spawns a new thread that starts up a socket server on a new port, say 5051.
From that time on the socket client and socket server communicate on port 5051. Either one can send data, in the form of a group of bytes, to the other.
Meanwhile the listener goes back to listening for connection requests on port 4040.

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Socket Client, Server, and Listener

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Client/Server Configuration

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Socket Data Transfer
The receiving socket, either client or server, has a

buffer that stores bytes of data until the receiver thread reads them.
If the receiver buffer is full, the sender thread will block on a send call until the receiver reads some of the data out of the buffer.
For this reason, it is a good idea to assign a thread in the receiver to empty the buffer and enqueue the data for a worker thread to digest.
If the receiver buffer becomes full during a send, the send request will return having sent less than the requested number of bytes.
If the receiving buffer is empty, a read request will block.
If the receiving buffer has data, but less than the number of bytes requested by a read, the call will return with the bytes available.

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Non-Blocking Communication

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Basic .Net Network Objects
TCPListener
TCPListener(port)
AcceptTcpClient()
AcceptSocket()
Start()
Stop()
Socket
Send(byte[], size, socketFlags)
Receive(byte[], size, socketFlags)
Close()
ShutDown(SocketShutDown)

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More Network Programming Objects
TCPClient
TCPClient()
Connect(IPAddress, port)
GetStream()
Close()
NetworkStream
NetworkStream(Socket)
Read(byte[], offset, size)
Write(byte[], offset, size)
You read and

write using the returned NetworkStream object

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Simple Socket Client
TcpClient tcpc = new TcpClient();
Byte[] read =

new Byte[32]; // read buffer
String server = args[0]; // server name
// Try to connect to the server
tcpc.Connect(server, 2048);
// Get a NetworkStream object
Stream s;
s = tcpc.GetStream();
// Read the stream and convert it to ASII
int bytes = s.Read(read, 0, read.Length);
String Time = Encoding.ASCII.GetString(read);
// Display the data
Console.WriteLine("\n Received {0} bytes", bytes);
Console.WriteLine(" Current date and time is: {0}", Time);
tcpc.Close();

Connects to server with this name

Connects to this server port

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Simple Socket Server
TcpListener tcpl = new TcpListener(2048); // listen on

port 2048
tcpl.Start();
while (true)
{
// Accept will block until someone connects
Socket s = tcpl.AcceptSocket();
// Get current date and time then concatenate it into a string
now = DateTime.Now;
strDateLine = now.ToShortDateString()
+ " " + now.ToLongTimeString();
// Convert the string to a Byte Array and send it
Byte[] byteDateLine = ASCII.GetBytes(strDateLine.ToCharArray());
s.Send(byteDateLine, byteDateLine.Length, 0);
s.Close();
Console.WriteLine("\n Sent {0}", strDateLine);
}

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Multi-threaded Server
If we want to support concurrent clients, the server must

spawn a thread for each new client.
C# Thread class makes that fairly simple.
Create a class that provides a non-static processing function. This is the code that serves each client.
Each time the TCPListener accepts a client it returns a socket. Pass that to the thread when it is constructed, and start the thread.

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$Define Thread’s Processing class threadProc { private Socket _sock = null;$

Define Thread’s Processing
class threadProc
{
private Socket _sock = null;

public threadProc(Socket sock)
{
_sock = sock;
}
public void proc()
{
for(int i=0; i<20; i++)
{
// Get the current date and time then concatenate it
// into a string
DateTime now = DateTime.Now;
string strDateLine = now.ToShortDateString() + " "
+ now.ToLongTimeString();
// Convert the string to a Byte Array and send it
Byte[] byteDateLine = Encoding.ASCII.GetBytes(strDateLine.ToCharArray());
_sock.Send(byteDateLine, byteDateLine.Length, 0);
Console.Write("\n Sent {0}", strDateLine);
Thread.Sleep(1000); // wait for one second just for demo
}
string QuitMessage = "Quit";
Byte[] byteQuit = Encoding.ASCII.GetBytes(QuitMessage.ToCharArray());
_sock.Send(byteQuit, byteQuit.Length, 0);
while(_sock.Connected)
Thread.Sleep(100);
_sock.Close();
}
}

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Server Spawns Threads to Handle New Clients with threadProc.proc()
// listen on port

2048
TcpListener tcpl = new TcpListener(2048);
tcpl.Start();
while (true)
{
// Accept will block until someone connects
Socket s = tcpl.AcceptSocket();
threadProc tp = new threadProc(s);
// pass threadProc.proc() function reference to
// ThreadStart delegate
Thread t = new Thread(new ThreadStart(tp.proc));
t.Start();
}

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Clients now Wait for Server to Complete
// Try to connect

to the server
tcpc.Connect(server, 2048);
// Get the NetworkStream object
Stream s;
s = tcpc.GetStream();
while(true)
{
// Read the stream and convert it to ASII
int bytes = s.Read(read, 0, read.Length);
String TSvrMsg = Encoding.ASCII.GetString(read);
TSrvMsg = TSrvMsg.Remove(bytes,TSrvMsg.Length-bytes);
// Display the data
if(TSrvMsg == "Quit")
{
Console.Write("\n Quitting");
break;
}
Console.WriteLine(" Server date and time is: {0}", TSrvMsg);
}
tcpc.Close();

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Talk Protocol
The hardest part of a client/server socket communication design is

to control the active participant
If single-threaded client and server both talk at the same time, their socket buffers will fill up and they both will block, e.g., deadlock.
If they both listen at the same time, again there is deadlock.
Often the best approach is to use separate send and receive threads
two unilateral communication channels
The next slide shows how to safely use bilateral communication.

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Bilateral Channel Talk-Listen Protocol

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Message Length
Another vexing issue is that the receiver may not know

how long a sent message is.
so the receiver doesn’t know how many bytes to pull from the stream to compose a message.
Often, the communication design will arrange to use message delimiters, fixed length messages, or message headers that carry the message length as a parameter.

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Message Framing
There are three solutions to this problem:
Use fixed length messages

– rarely useful
Use fixed length message headers
Encode message body length in header
Reader pulls header, parses to find length of rest of message and pulls it.
Use message termination sentinals
body of message
Reader reads a character at a time out of channel
Adds character to message
Scans message from back looking for to conclude message extraction.

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They’re Everywhere
Virtually every network and internet communication method uses sockets, often

in a way that is invisible to an application designer.
Browser/server
ftp
SOAP
Network applications

Net Sockets

Содержание

Referenceswww.msdn.microsoft.com/library.Net Development/.Net Framework SDK/.Net Framework/Reference/ClassLibrary/System.Net.Sockets http://www.dotnetjunkies.com/quickstart/howto/doc/TCPUDP/DateTimeClient.aspxC# NetworkProgramming, Richard Blum, Sybex, 2003 Win32 Sockets,

What are Sockets?Sockets provide a common interface to the various protocols

Socket Logical Structure

How do Sockets Function?There are several modes of operation available for

Socket Client, Server, and Listener

Client/Server Configuration

Socket Data TransferThe receiving socket, either client or server, has a

Non-Blocking Communication

Basic .Net Network ObjectsTCPListenerTCPListener(port)AcceptTcpClient()AcceptSocket()Start()Stop() SocketSend(byte[], size, socketFlags)Receive(byte[], size, socketFlags)Close()ShutDown(SocketShutDown)

More Network Programming ObjectsTCPClientTCPClient()Connect(IPAddress, port)GetStream()Close() NetworkStreamNetworkStream(Socket)Read(byte[], offset, size)Write(byte[], offset, size)You read and

Simple Socket Client TcpClient tcpc = new TcpClient(); Byte[] read =

Simple Socket Server TcpListener tcpl = new TcpListener(2048); // listen on

Multi-threaded ServerIf we want to support concurrent clients, the server must

Define Thread’s Processing class threadProc { private Socket _sock = null;

Server Spawns Threads to Handle New Clients with threadProc.proc()// listen on port

Clients now Wait for Server to Complete // Try to connect

Talk ProtocolThe hardest part of a client/server socket communication design is