关于RTF发送文字、图片的问题

最近在写一个局域网聊天工具，普通richtxtbox发送文字没问题。后来导入了类似QQ表情的控件，于是乎，问题出来了，图片发送不了。
网上找了办法，说是用richtxtbox.rtf替代richtxtbox.Text。但是小弟整了好几天，依旧没法解决。祈求高手。接收数据代码：if (this.gifRichTextBox1.Text != "")
                                {
                                    this.gifRichTextBox1.Text = gifRichTextBox1.Text + "\n" + this.TBIp.Text + ":" + msg.Substring(3) + "    GetData";
                                }
                                else
                                {
                                    this.gifRichTextBox1.Text = this.TBIp.Text + ":" + msg.Substring(3) + "    GetData";
                                }
发送数据：
 public void SendData(string m)
        {
           // string msg = this.gifRichTextBox2.Text;
            string msg = m;
            if (msg != "")
            {
                IPEndPoint pp = new IPEndPoint(IPAddress.Parse(i), port);
                Socket client = new Socket(AddressFamily.InterNetwork,
                        SocketType.Dgram, ProtocolType.Udp);
                try
                {
                    client.Connect(pp);                    byte[] buff = Encoding.Default.GetBytes(msg);
                    client.Send(buff);
                }
                catch
                {
                    client.Shutdown(SocketShutdown.Receive);
                    client.Close();
                }
            }
        }