socket 为什么发送第一次成功 第二次 不成功呢？？？

 private void button1_Click(object sender, EventArgs e)
        {
            try            
            {                 
                int port = 2000;                
                string host = '192.168.0.127';                
                IPAddress ip = IPAddress.Parse(host);                
                IPEndPoint ipe = new IPEndPoint(ip, port);//把ip和端口转化为IPEndPoint实例  

                c = null;
                c = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);//创建一个Socket
                              
                c.Connect(ipe);//连接到服务器  
            }           
            catch (ArgumentNullException a)
            {
                MessageBox.Show(String.Format('ArgumentNullException:{0}', a));
            }            
            catch (SocketException a)
            {
                MessageBox.Show(String.Format('SocketException:{0}', a.Message));
            }
        }

发送数据代码

private void button2_Click(object sender, EventArgs e)
        {
            string sendStr = 'hello!This is a socket test';
            byte[] bs = Encoding.ASCII.GetBytes(sendStr);
            
            c.Send(bs, bs.Length, 0);//发送测试信息                
            string recvStr = '';
            byte[] recvBytes = new byte[1024];
            int bytes;
            
            bytes = c.Receive(recvBytes, recvBytes.Length, 0);//从服务器端接受返回信息               
            if (bytes <= 0)
                return;
            recvStr = Encoding.ASCII.GetString(recvBytes, 0, bytes);
           
               if(recvStr!='')
               {
                   richTextBox1.Text += '有数据！\r\n';
                   richTextBox1.ScrollToCaret();
               }
               else
               {
                   
               }
            Thread.Sleep(100);