socket error in winform application

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C#

actually i have develop the network project in winforms.

my problem is socket error in one form(router form) that socket error like


"system.argumentNullException:value can not be null.
parameter name:buffer
at system.Net.Sockets.socket.Send(Byte[]buffer,int32 offset,int32size,SocketFlags socketFlags,SocketError&errorCode)
at system.Net.Sockets.socket.Send(Byte[]buffer,int32 offset,int32size,SocketFlags socketFlags)
at system.Net.Sockets.socket.Send(Byte[]buffer)
at simulation.routers.send()in c:\Documentandsettings\Adminstrator\desktop\sourcecode\routers\router.cs:line 51"

socket error occur in send method like as

private void Send()
        {
            try
            {
                IPAddress[] ipAddress = Dns.GetHostAddresses(textBox1.Text);
                IPEndPoint ipEnd = new IPEndPoint(ipAddress[0], 5656);
                Socket clientSock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP);

                clientSock.Connect(ipEnd);
                clientSock.Send(ReceiverCode.send);
                clientSock.Close();

            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString());
            }
        }

in this method contain error statement

clientSock.Send(ReceiverCode.send);

this project had completed using wireless network(wi-fi)on yesterday.

but today morning my wifi not working then i have run the project using another wifi and local

area connection but still my project have socket error

pls help me