问题
With regards to handling a TCP/IP connection using the TcpClient
class, is there an alternative for checking whether the remote host has closed the connection other than waiting for the NetworkStream.Read
method to return a 0?
回答1:
You can use IOControlCode.KeepAliveValues
on the TcpClient.Client
to guarantee that a keep-alive check is made at least on the specified interval and then check the TcpClient.Client.Connected
property.
An example how to use it:
struct tcp_keepalive
{
public int OnOff;
public int KeepAliveTime;
public int KeepAliveInterval;
public unsafe byte[] Buffer
{
get
{
var buf = new byte[sizeof(tcp_keepalive)];
fixed(void* p = &this) Marshal.Copy(new IntPtr(p), buf, 0, buf.Length);
return buf;
}
}
};
static void KeepAliveTest()
{
using(var c = new TcpClient())
{
c.Connect("www.google.com", 80);
var s = c.Client;
var ka = new tcp_keepalive();
ka.OnOff = 1; // enable
ka.KeepAliveTime = 1000 * 60; // 60 seconds of inactivity allowed
ka.KeepAliveInterval = 1000; // 1 second interval on keep-alive checks (default)
s.IOControl(IOControlCode.KeepAliveValues, ka.Buffer, null);
var ns = c.GetStream();
Console.WriteLine("Connected to " + s.RemoteEndPoint);
while(true)
{
SocketError se;
s.Blocking = false;
s.Receive(new byte[0], 0, 0, SocketFlags.Peek, out se);
s.Blocking = true;
if(!s.Connected)
{
// se==SocketError.ConnectionReset||SocketError.NetworkReset if the connection was closed because of a keep-alive check
Console.WriteLine("Socket disconnected: " + se);
break;
}
// do other stuff
if(ns.DataAvailable) ns.Read(new byte[100], 0, 100);
else Thread.Sleep(10);
}
}
}
来源:https://stackoverflow.com/questions/1993635/alternative-to-networkstream-read-that-indicates-remote-host-has-closed-the-conn