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ProtocolType Enumeration

Specifies the protocols that the Socket class supports.

Namespace:  System.Net.Sockets
Assembly:  System (in System.dll)

public enum ProtocolType

Member nameDescription
IPInternet Protocol.
IPv6HopByHopOptionsIPv6 Hop by Hop Options header.
IcmpInternet Control Message Protocol.
IgmpInternet Group Management Protocol.
GgpGateway To Gateway Protocol.
IPv4Internet Protocol version 4.
TcpTransmission Control Protocol.
PupPARC Universal Packet Protocol.
UdpUser Datagram Protocol.
IdpInternet Datagram Protocol.
IPv6Internet Protocol version 6 (IPv6).
IPv6RoutingHeaderIPv6 Routing header.
IPv6FragmentHeaderIPv6 Fragment header.
IPSecEncapsulatingSecurityPayloadIPv6 Encapsulating Security Payload header.
IPSecAuthenticationHeaderIPv6 Authentication header. For details, see RFC 2292 section 2.2.1, available at
IcmpV6Internet Control Message Protocol for IPv6.
IPv6NoNextHeaderIPv6 No next header.
IPv6DestinationOptionsIPv6 Destination Options header.
NDNet Disk Protocol (unofficial).
RawRaw IP packet protocol.
UnspecifiedUnspecified protocol.
IpxInternet Packet Exchange Protocol.
SpxSequenced Packet Exchange protocol.
SpxIISequenced Packet Exchange version 2 protocol.
UnknownUnknown protocol.

The Socket class uses the ProtocolType enumeration to inform the Windows Sockets API of the requested protocol. Low-level driver software for the requested protocol must be present on the computer for the Socket to be created successfully.

The following example demonstrates how to use ProtocolType to instantiate a Socket.

using System;
using System.Text;
using System.IO;
using System.Net;
using System.Net.Sockets;

public class Sample

  public static string DoSocketGet(string server) 
    //Set up variables and String to write to the server.
    Encoding ASCII = Encoding.ASCII;
    string Get = "GET / HTTP/1.1\r\nHost: " + server + 
                 "\r\nConnection: Close\r\n\r\n";
    Byte[] ByteGet = ASCII.GetBytes(Get);
    Byte[] RecvBytes = new Byte[256];
    String strRetPage = null;

    // IPAddress and IPEndPoint represent the endpoint that will
    //   receive the request.
    // Get first IPAddress in list return by DNS.


      // Define those variables to be evaluated in the next for loop and 
      // then used to connect to the server. These variables are defined
      // outside the for loop to make them accessible there after.
      Socket s = null;
      IPEndPoint hostEndPoint;
      IPAddress hostAddress = null;
      int conPort = 80;

      // Get DNS host information.
      IPHostEntry hostInfo = Dns.GetHostEntry(server);
      // Get the DNS IP addresses associated with the host.
      IPAddress[] IPaddresses = hostInfo.AddressList;

      // Evaluate the socket and receiving host IPAddress and IPEndPoint. 
      for (int index=0; index<IPaddresses.Length; index++)
        hostAddress = IPaddresses[index];
        hostEndPoint = new IPEndPoint(hostAddress, conPort);

        // Creates the Socket to send data over a TCP connection.
        s = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp );

        // Connect to the host using its IPEndPoint.

        if (!s.Connected)
          // Connection failed, try next IPaddress.
          strRetPage = "Unable to connect to host";
          s = null;

        // Sent the GET request to the host.
        s.Send(ByteGet, ByteGet.Length, 0);

      } // End of the for loop.      

      // Receive the host home page content and loop until all the data is received.
      Int32 bytes = s.Receive(RecvBytes, RecvBytes.Length, 0);
      strRetPage = "Default HTML page on " + server + ":\r\n";
      strRetPage = strRetPage + ASCII.GetString(RecvBytes, 0, bytes);

      while (bytes > 0)
        bytes = s.Receive(RecvBytes, RecvBytes.Length, 0);
        strRetPage = strRetPage + ASCII.GetString(RecvBytes, 0, bytes);

    } // End of the try block.

    catch(SocketException e) 
      Console.WriteLine("SocketException caught!!!");
      Console.WriteLine("Source : " + e.Source);
      Console.WriteLine("Message : " + e.Message);
    catch(ArgumentNullException e)
      Console.WriteLine("ArgumentNullException caught!!!");
      Console.WriteLine("Source : " + e.Source);
      Console.WriteLine("Message : " + e.Message);
    catch(NullReferenceException e)
      Console.WriteLine("NullReferenceException caught!!!");
      Console.WriteLine("Source : " + e.Source);
      Console.WriteLine("Message : " + e.Message);
    catch(Exception e)
      Console.WriteLine("Exception caught!!!");
      Console.WriteLine("Source : " + e.Source);
      Console.WriteLine("Message : " + e.Message);

    return strRetPage;

   public static void Main()

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Community Additions

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