Figure 1

Figure 1 .NET Framework Features

Figure 5 C# Server Code for a Web Service

  <%@ WebService Language="C#" Class="P2PService" %>

public class P2PService : WebService 
{
    public static ArrayList PeerFiles;    
    private static String MyLock = "lock";
    // For the sake of simplicity, this sample is using an ArrayList
    // to store peer information in memory.
    // This information could be stored in a file, database, or by some 
    // other means.
    
    P2PService() 
    {
                
        if( null == PeerFiles) 
        {
            lock(MyLock) 
            {
                if( null == PeerFiles )
                    PeerFiles = new ArrayList();
            }
        }        
    }

    [WebMethod]
    public int GetNumUsers()
    {        
        // Get the count of all registered users

        return users.Count;
    }    

    [WebMethod]
    public int ClearEntriesForPeer(string hostname)
    {            
        // Unregister code goes here                    
        return NumEntriesCleared;
    }    


    [WebMethod]
    public int GetNumFiles()
    {                
        return PeerFiles.Count;
    }    
    
    [WebMethod]
    public int RegisterFile(string hostname, string name, 
                            string connection, string size)
    {        
        // Registration code here        
        return PeerFiles.Count;
    }

    [WebMethod] 
    public PeerFile[] GetPeerFilesInfo()
    {
        return (PeerFile[])PeerFiles.ToArray(typeof(PeerFile));
    } 
    
    [WebMethod]
    public PeerFile[] FindPeersWithFiles(string Search)
    {
        // Lookup code goes here
        
        return (PeerFile[])MatchingPeers.ToArray(typeof(PeerFile));
    }
}

public class PeerFile : IComparable
{    
    public string IpAddress;
    public string Name;
    public string Connection;
    public string Size;    
}

Figure 6 P2PService Class

Figure 7 C# Client Code for the Web Service

  // Using the Web Service client proxy code to hit the service

//Get other servers
P2Pservice  s = new P2PService();

// Register a file with the service
s.RegisterFile("dnsname", "Service Information.doc", "Cable", "29423");

// Get the number of other peers registered
int NumPeers = s.GetNumPeers();

// Query the service for some content
PeerFile[] Files = s.FindPeersWithFiles("foo");

// Unregister files from the service
int NumFilesUnregistered = s.ClearEntriesForPeer("dnsname");

Figure 8 Peer Sending the File

  public void ListenForPeers() 
{                    
    try
    {  
          
        Encoding ASCII = Encoding.ASCII;     
                        
        tcpl.Start();                                

        while (true)
        {        
            // Accept will block until someone connects  
            Socket s = tcpl.Accept();                        
            NetworkStream DataStream = new NetworkStream(s);

            String filename;
            Byte[] Buffer = new Byte[256];
            DataStream.Read(Buffer, 0, 256);
            filename = Encoding.ASCII.GetString(Buffer);
            StringBuilder sbFileName = new StringBuilder(filename);
            StringBuilder sbFileName2 = sbFileName.Replace("\\", "\\\\");
            FileStream fs = new FileStream(sbFileName2.ToString(),
                                         FileMode.Open, FileAccess.Read);  
            BinaryReader reader = new BinaryReader(fs);
            byte[] bytes = new byte[1024];
            int read;
            while((read = reader.Read(bytes, 0, bytes.Length)) != 0) 
            {
                // Read from the file and write the data to the network
                DataStream.Write(bytes, 0, read);
            }
            reader.Close();    
            DataStream.Flush();
            DataStream.Close();
        }
    }
    catch(SocketException ex)
    {                
        MessageBox.Show(ex.ToString());
    }
}

Figure 9 Peer Receiving the File

  public void DownloadToClient(String server, string remotefilename, 
                             string localfilename) 
{
    try
    {
        TCPClient tcpc = new TCPClient();                
        Byte[] read = new Byte[1024];                          
        
        // Try to connect to the server                
        if (tcpc.Connect(server, 8081) == -1) 
        {                
            return;
        }
        
        // Get the stream
        Stream s = tcpc.GetStream();    
        Byte[] b = Encoding.ASCII.GetBytes(remotefilename.ToCharArray());
        s.Write( b, 0,  b.Length );
        int bytes;
        FileStream fs = new FileStream(localfilename, 
                                       FileMode.OpenOrCreate);
        BinaryWriter w = new BinaryWriter(fs);

        // Read the stream            
        while( (bytes = s.Read(read, 0, read.Length)) != 0) 
        {             
            w.Write(read, 0, bytes);
            read = new Byte[1024];                
        }               

        tcpc.Close();
        w.Close();
        fs.Close();
    }
    catch(Exception ex)
    {        
        MessageBox.Show(ex.ToString());
    }
}

Figure 10 Downloading HTML Content

  // Create a WebRequest object passing in the desired URI to the .Create() 
// method and then 
// get a response from the server by calling .GetResponse();
WebRequest WReq = WebRequestFactory.Create("https://www.mypeer-to-  
                                           peer.com/news.htm");
WebResponse WResp = WReq.GetResponse();

// Get a readable stream from the server - Encode the data to ASCII for 
// writing to the console
StreamReader sr = new StreamReader(WResp.GetResponseStream(), 
                                   Encoding.ASCII);

// Declare vars used for reading text
int length = 1024;
char [] Buffer = new char[1024];
int bytesread = 0;      

//Read from the stream and write any data to the console
bytesread = sr.Read( Buffer, 0, length);
while( bytesread > 0 ) 
{
    // If your application is a Windows Forms application, you might
    // append this data using a StringBuilder and then hand the data
    // to an HTML rendering control once it has all been downloaded.
    Console.Write( Buffer,0, bytesread);    
    bytesread = sr.Read( Buffer, 0, length);
}

//Close the stream when finished
sr.Close();
Wresp.GetResponseStream().Close();