Networking

1
Networking

• Web services
• Also a type of networking
• HTTP
• System.Net.WebRequest
• System.Net.WebResponse
• TCP/IP
• System.Net.Sockets.Socket
• Infrared communications
• Serial communications

2
Simple HTTP request/response

• WebRequest and WebResponse
• inside System.Net namespace
• abstract classes
• Cant create an instance using constructor
• Use WebRequest.Create(url)
• Return an instance of HTTPWebRequest if url
  starts with http// or https//
• Example

using System.Net using System.IO . . WebRequest
reqWebRequest.Create(uri) WebResponse
resreq.GetResponse()
3
Sample HTTP code

• HttpGetSample
• Error handling
• WebException
• Errors returned by the server
• UriFormatException

4
Accessing HTTP headers

• Properties
• Accept lt-gt HttpWebRequest.Accept
• User-Agent lt-gt HttpWebRequest.User-Agent
• Server lt-gt HttpWebResponse.Server
• System.Net.WebHeaderCollection

HttpWebRequest req (HttpWebRequest)
WebRequest.Create(uri) req.Headers.Add(User-Agen
t, dotNETCF Test Program) HttpWebResponse
res (HttpWebResponse) req.GetResponse() String
server res.Headersservers
5
HTTP GET

• Send data in query string
• ?FirstNameAndyLastNameWigley
• Special characters need to be encoded
• ? -gt 3f
• / -gt 3f
• Space -gt
• .Net Compact Framework does not have utility to
  do encoding and decoding

6
HTTP POST
public void doPost(String url, String payload)
WebRequest req WebRequest.Create(url)
req.Method POST req.ContentType
text/plain charsetutf-8 // Encode the
data byte encodedBytes
Encoding.UTF8.GetBytes(payload)
req.ContentLength encodedBytes.Length //
write encoded data into request stream
Stream requestStream req.GetRequestStream()
requestStream.Write(encodedBytes, 0,
encodedBytes.Length) requestStream.Close()
WebResponse result req.GetResponse()
7
Working with Sockets

• System.Net.Sockets
• Managed implementation of winsock for .NET
  framework
• TcpListener and TcpClient
• blocking synchronous transfer
• Socket class
• asynchronous transfer
• UdpClient class

8
System.Net.Sockets.TcpListener

• Listen on a particular port
• TcpListener tcpServer new
  TcpListener(695)
• Listen on the port assigned by the system
• TcpListener tcpServer new TcpListener(0)
• tcpServer.Start()
• System.Net.IPEndPoint assignedEndpoint
  (System.Net.IPEndPoint) tcpServer.LocalEndPoint
• int localport assignedEndPoint.Port
• Create IPEndPoint object and pass into
  TcpListener constructor
• IPEndPoint endPt new
  IPEndPoint(IPAddress.Parse(192.168.0.1), 695)
• TcpListener tcpServer new
  TcpListener(endPt)

9
TcpListenerSample Example

• TcpClient offers methods to send and receive
  data
• TcpClient.Connect() make a connection to the
  server
• TcpClient.GetStream returns the IO stream

10
System.Net.Sockets.UdpClient

• To send a datagram
• UdpClient udpClient new UdpClient()
• byte msgBytes
• System.Text.Encoding.ASCII.GetBytes(Message)
  
• udpClient.Send(msgBytes, msgBytes.Length,
• 192.168.1.101,
  6950)
• To receive a datagram, use udpClient.Receive()