C# 中如何判断一台主机是否在线?
try···chtch就免了。
try···chtch就免了。
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http://www.csharphelp.com/archives/archive6.html不过有些主机的防火墙是不允许IGMP请求的,比如XP SP2的默认设置,这样也没法
http://www.csharphelp.com/archives/archive6.html
这个上面的代码有问题,但你ping一个不存在的主机时它就停顿了。
我测试了下,是nBytes = socket.ReceiveFrom(ReceiveBuffer, 256, 0, ref EndPointFrom);
这一句的问题,不知,你们还有没有什么好的办法
// 返回 Host not found
PingHost("www.163.com");
// 返回 Reply from 202.108.36.153:0 in 47MS :Bytes Received60没有问题的啊
他的代码是基于.NET beta的,有几个地方语法不对,对应改过来就是了
/// This method takes the "hostname" of the server
/// and then it ping's it and shows the response time
/// </summary>
public static void PingHost(string host)
{
//Declare the IPHostEntry
IPHostEntry serverHE, fromHE;
int nBytes = 0;
int dwStart = 0, dwStop = 0;
//Initilize a Socket of the Type ICMP
Socket socket =
new Socket(AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp); // Get the server endpoint
try
{
serverHE = Dns.GetHostByName(host);
}
catch(Exception)
{
Console.WriteLine("Host not found"); // fail
return ;
} // Convert the server IP_EndPoint to an EndPoint
IPEndPoint ipepServer = new IPEndPoint(serverHE.AddressList[0], 0);
EndPoint epServer = (ipepServer); // Set the receiving endpoint to the client machine
fromHE = Dns.GetHostByName(Dns.GetHostName());
IPEndPoint ipEndPointFrom = new IPEndPoint(fromHE.AddressList[0], 0);
EndPoint EndPointFrom = (ipEndPointFrom); int PacketSize = 0;
IcmpPacket packet = new IcmpPacket();
// Construct the packet to send
packet.Type = ICMP_ECHO; //8
packet.SubCode = 0;
packet.CheckSum = UInt16.Parse("0");
packet.Identifier = UInt16.Parse("45");
packet.SequenceNumber = UInt16.Parse("0");
int PingData = 32; // sizeof(IcmpPacket) - 8;
packet.Data = new Byte[PingData];
//Initilize the Packet.Data
for (int i = 0; i < PingData; i++)
{
packet.Data[i] = (byte)'#';
} //Variable to hold the total Packet size
PacketSize = PingData + 8;
Byte [] icmp_pkt_buffer = new Byte[ PacketSize ];
Int32 Index = 0;
//Call a Method Serialize which counts
//The total number of Bytes in the Packet
Index = Serialize(
packet,
icmp_pkt_buffer,
PacketSize,
PingData );
//Error in Packet Size
if( Index == -1 )
{
Console.WriteLine("Error in Making Packet");
return ;
} // now get this critter into a UInt16 array //Get the Half size of the Packet
Double double_length = Convert.ToDouble(Index);
Double dtemp = Math.Ceiling( double_length / 2);
int cksum_buffer_length = Convert.ToInt32(dtemp);
//Create a Byte Array
UInt16 [] cksum_buffer = new UInt16[cksum_buffer_length];
//Code to initialize the Uint16 array
int icmp_header_buffer_index = 0;
for( int i = 0; i < cksum_buffer_length; i++ )
{
cksum_buffer[i] =
BitConverter.ToUInt16(icmp_pkt_buffer,icmp_header_buffer_index);
icmp_header_buffer_index += 2;
}
//Call a method which will return a checksum
UInt16 u_cksum = checksum(cksum_buffer, cksum_buffer_length);
//Save the checksum to the Packet
packet.CheckSum = u_cksum;
// Now that we have the checksum, serialize the packet again
Byte [] sendbuf = new Byte[ PacketSize ];
//again check the packet size
Index = Serialize(
packet,
sendbuf,
PacketSize,
PingData );
//if there is a error report it
if( Index == -1 )
{
Console.WriteLine("Error in Making Packet");
return ;
}
dwStart = System.Environment.TickCount; // Start timing
//send the Pack over the socket
if ((nBytes = socket.SendTo(sendbuf, PacketSize, 0, epServer)) == SOCKET_ERROR)
{
Console.WriteLine("Socket Error cannot Send Packet");
}
// Initialize the buffers. The receive buffer is the size of the
// ICMP header plus the IP header (20 bytes)
Byte [] ReceiveBuffer = new Byte[256];
nBytes = 0;
//Receive the bytes
bool recd =false ;
int timeout=0 ; //loop for checking the time of the server responding
while(!recd)
{
nBytes = socket.ReceiveFrom(ReceiveBuffer, 256, 0, ref EndPointFrom);
if (nBytes == SOCKET_ERROR)
{
Console.WriteLine("Host not Responding") ;
recd=true ;
break;
}
else if(nBytes>0)
{
dwStop = System.Environment.TickCount - dwStart; // stop timing
Console.WriteLine("Reply from "+epServer.ToString()+" in "
+dwStop+"MS :Bytes Received"+nBytes);
recd=true;
break;
}
timeout=System.Environment.TickCount - dwStart;
if(timeout>1000)
{
Console.WriteLine("Time Out") ;
recd=true;
}
}
//close the socket
socket.Close();
}
/// <summary>
/// This method get the Packet and calculates the total size
/// of the Pack by converting it to byte array
/// </summary>
public static Int32 Serialize(IcmpPacket packet, Byte[] Buffer,
Int32 PacketSize, Int32 PingData )
{
Int32 cbReturn = 0;
// serialize the struct into the array
int Index=0; Byte [] b_type = new Byte[1];
b_type[0] = (packet.Type); Byte [] b_code = new Byte[1];
b_code[0] = (packet.SubCode); Byte [] b_cksum = BitConverter.GetBytes(packet.CheckSum);
Byte [] b_id = BitConverter.GetBytes(packet.Identifier);
Byte [] b_seq = BitConverter.GetBytes(packet.SequenceNumber);
// Console.WriteLine("Serialize type ");
Array.Copy( b_type, 0, Buffer, Index, b_type.Length );
Index += b_type.Length;
// Console.WriteLine("Serialize code ");
Array.Copy( b_code, 0, Buffer, Index, b_code.Length );
Index += b_code.Length; // Console.WriteLine("Serialize cksum ");
Array.Copy( b_cksum, 0, Buffer, Index, b_cksum.Length );
Index += b_cksum.Length; // Console.WriteLine("Serialize id ");
Array.Copy( b_id, 0, Buffer, Index, b_id.Length );
Index += b_id.Length; Array.Copy( b_seq, 0, Buffer, Index, b_seq.Length );
Index += b_seq.Length; // copy the data
Array.Copy( packet.Data, 0, Buffer, Index, PingData );
Index += PingData;
if( Index != PacketSize/* sizeof(IcmpPacket) */)
{
cbReturn = -1;
return cbReturn;
} cbReturn = Index;
return cbReturn;
}
/// <summary>
/// This Method has the algorithm to make a checksum
/// </summary>
public static UInt16 checksum( UInt16[] buffer, int size )
{
Int32 cksum = 0;
int counter;
counter = 0; while ( size > 0 )
{
// UInt16 val = buffer[counter]; cksum += Convert.ToInt32( buffer[counter] );
counter += 1;
size -= 1;
} cksum = (cksum >> 16) + (cksum & 0xffff);
cksum += (cksum >> 16);
return (UInt16)(~cksum);
}
你PingHost个不存在的ip试试.你ping 的那个是不存在的域名
比如说:pingHost("222.222.222.222");
最简单的可以改成多线程的,如果不想对他的代码做太大的改动:static string host = "128.0.0.1";static void Main(string[] argv)
{
TimeSpan timeOut = new TimeSpan(0,0,15); Thread pingThread = new Thread(new ThreadStart(PingHost));
pingThread.IsBackground = true;
pingThread.Priority = ThreadPriority.Highest;
pingThread.Start();
pingThread.Join(timeOut); Console.WriteLine("Done");
Console.ReadLine();
return;
}然后把PingHost函数host参数去掉:
static void PingHost()这样在15秒内如果一直没响应,则可以判定为主机不存在在socket编程,多线程/异步,必选其一
SystemInformation.Network 属性
不同的用途可能会用到不同的方法