[转]c# winform tcp connect timeout 连接超时设置

转自:https://www.cnblogs.com/jhlong/p/5622336.html

简单的c# TCP通讯（TcpListener）

C# 的TCP Socket （同步方式）

C# 的TCP Socket （异步方式）

C# 的tcp Socket设置自定义超时时间

C# TCP socket发送大数据包时，接收端和发送端数据不一致 服务端接收Receive不完全

方式一

tcp Socket的超时时间默认20多秒，而实际连上不需1秒时间，20多秒是无法接受的。

private delegate string ConnectSocketDelegate(IPEndPoint ipep, Socket sock);
private string ConnectSocket(IPEndPoint ipep, Socket sock)
{
string exmessage = "";
try
{
sock.Connect(ipep);
}
catch (System.Exception ex)
{
exmessage = ex.Message;
}
finally
{
}

return exmessage;
}
private void button5_Click_1(object sender, EventArgs e)
{

IPEndPoint ipep = new IPEndPoint(IPAddress.Parse("192.168.18.165"), 9961);//IP和端口
Socket sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

ConnectSocketDelegate connect = ConnectSocket;
IAsyncResult asyncResult = connect.BeginInvoke(ipep, sock, null, null);

bool connectSuccess = asyncResult.AsyncWaitHandle.WaitOne(2000, false); //2秒后结束
if (!connectSuccess)
{
MessageBox.Show(string.Format("失败！错误信息：{0}", "连接超时"));//2秒后弹出

}

string exmessage = connect.EndInvoke(asyncResult); //此处仍然会卡住20多秒,可注释掉
if (!string.IsNullOrEmpty(exmessage))
{
MessageBox.Show(string.Format("失败！错误信息：{0}", exmessage));

}

}

方式二:修改注册表(亲测有效)

HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTcpipParameters

Value Name:  TcpMaxDataRetransmissions
Data Type:   REG_DWORD - Number
Valid Range: 0 - 0xFFFFFFFF
Default:     2  (默认值5 修改为2)

Description: This parameter controls the number of times TCP retransmits an individual data segment (non connect segment) 
before aborting the connection. The retransmission time-out is doubled with each successive retransmission on a connection. 
It is reset when responses resume. The base time-out value is dynamically determined by the measured round-trip time on the connection.

Value Name:  InitialRttData 
Type:   REG_DWORD
Valid Range: 0-65535 (decimal)
Default:     0x5dc (1500毫秒 默认值 0xBB8 (3000 decimal) )

Description: This parameter controls the initial retransmission time-out used by TCP on each new connection. It applies to the connection request (SYN) and to the first data segment(s) sent on each connection.

超时时间大概是2*1.5s
来源 https://support.microsoft.com/en-us/help/170359/how-to-modify-the-tcp-ip-maximum-retransmission-time-out