简单的网络心跳包实现（如何确保client在线）

接受：
case "Bit":
string ipAndport = splitString[1].Trim() + ":" + splitString[2].Trim();
BitUpdate(ipAndport);
break;
发送：
private delegate void BitUpdateDele(string ipAndport);
/// <summary>
/// 收到Bit包，修改心跳包标志为0
/// </summary>
private void BitUpdate(string ipAndport)
{
if (lvwUser.InvokeRequired)
{
BitUpdateDele d = BitUpdate;
lvwUser.Invoke(d, ipAndport);
}
else
{
for (int i = 0; i < lvwUser.Items.Count; i++)
{
if (lvwUser.Items[i].SubItems[1].Text == ipAndport)
{
lvwUser.Items[i].SubItems[2].Text = "0";
break;
}
}
}
}
private delegate void BitDele();
/// <summary>
/// 发送Bit包之前，修改心跳包标志，0--1，1++
/// </summary>
private void Bit()
{
if (lvwUser.InvokeRequired)
{
BitDele d = Bit;
lvwUser.Invoke(d);
}
else
{
for (int i = 0; i < lvwUser.Items.Count; i++)
{
if (lvwUser.Items[i].SubItems[1].Text != localIp.ToString() + ":" + port.ToString())
{
string temp = lvwUser.Items[i].SubItems[2].Text;
if (temp == "0")
lvwUser.Items[i].SubItems[2].Text = "1";
else
{
lvwUser.Items[i].SubItems[2].Text = (int.Parse(temp) + 1).ToString();
}
}
}
}
}
/// <summary>
/// 每隔2秒，进行Bit包发送
/// </summary>
private void timer1_Tick(object sender, EventArgs e)
{
Bit();
string Bit = "Bit," + localIp.ToString() + "," + port.ToString();
SendMessage(localIp,Bit);
}
/// <summary>
/// 进行判断，如果心跳包标志大于3时，说明已经离线删除用户
/// </summary>
private void BitJudge()
{
if (lvwUser.InvokeRequired)
{
BitDele d = Bit;
lvwUser.Invoke(d);
}
else
{
for (int i = 0; i < lvwUser.Items.Count; i++)
{
string temp = lvwUser.Items[i].SubItems[2].Text;
if (int.Parse(temp) > 3)
lvwUser.Items.RemoveAt(i);
}
}
}
private void timer2_Tick(object sender, EventArgs e)
{
BitJudge();
}