I am trying to write code the receives broadcast messages coming from another app. using wireShark, I can see that they are sent to 255.255.255.255:300.
I tried the following code:
IPEndPoint ServerEndPoint = new IPEndPoint(IPAddress.Any, 3000);
Socket WinSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
WinSocket.Bind(ServerEndPoint);
byte[] data = new byte[10];
Console.Write("Waiting for client");
IPEndPoint sender = new IPEndPoint(IPAddress.Any, 0);
EndPoint Remote = (EndPoint)(sender);
int recv = WinSocket.ReceiveFrom(data, ref Remote);
Console.WriteLine("Message received from {0}:", Remote.ToString());
string str = Encoding.ASCII.GetString(data, 0, recv);
but when my app reached to the "bind" command there is an error message:
"Only one usage of each socket address (protocol/network address/port) is normally permitted"
if I change the port there is no error but I catch nothing.
Please advice
Related
I have found this piece of code on the internet: it does not open a server listening on port 11000, as I hoped.
What can be the problem? I normally code in Delphi, so I am little lost. I have made a corresponding client in Delphi, which works.
I am using demo version of C# 2015.
public static void StartListening()
{
// Data buffer for incoming data.
byte[] bytes = new Byte[1024];
// Establish the local endpoint for the socket.
// Dns.GetHostName returns the name of the
// host running the application.
IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());
IPAddress ipAddress = ipHostInfo.AddressList[0];
IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 11000);
// Create a TCP/IP socket.
Socket listener = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp);
// Bind the socket to the local endpoint and
// listen for incoming connections.
try
{
listener.Bind(localEndPoint);
listener.Listen(10);
// Start listening for connections.
while (true)
{
//Console.WriteLine("Waiting for a connection...");
// Program is suspended while waiting for an incoming connection.
Socket handler = listener.Accept();
data = null;
// An incoming connection needs to be processed.
while (true)
{
bytes = new byte[1024];
int bytesRec = handler.Receive(bytes);
data += Encoding.ASCII.GetString(bytes, 0, bytesRec);
if (data.IndexOf("#") > -1)
{
break;
}
}
// Show the data on the console.
//Console.WriteLine("Text received : {0}", data);
// Echo the data back to the client.
byte[] msg = Encoding.ASCII.GetBytes(data);
handler.Send(msg);
handler.Shutdown(SocketShutdown.Both);
handler.Close();
}
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
//Console.WriteLine("\nPress ENTER to continue...");
//Console.Read();
}
The problem might be here: Whats the IP address of ipHostInfo.AddressList[0] ? It might be the loop-back. I never restrict my server endpoint to an ip-adress unless I need to, but then I will specify it in a configfile.
IPEndPoint localEndPoint = new IPEndPoint(IPAddress.Any, 11000);
As per Jeroen's answer, encountered per .NET's Synchronous Server Socket Example. When listening/connecting to localhost, one should rather use
IPAddress ipAddress = IPAddress.Parse("127.0.0.1");
instead of
// Establish the local endpoint for the socket.
// Dns.GetHostName returns the name of the
// host running the application.
IPHostEntry ipHostInfo = Dns.GetHostEntry(Dns.GetHostName());
IPAddress ipAddress = ipHostInfo.AddressList[0];
Thanks for feedback. I found som other, older code:
TcpListener serverSocket = new TcpListener(11000);
that does the job. I know it is depreciated, but it works, actually.
The following code sends a packet on port 15000:
int port = 15000;
UdpClient udp = new UdpClient();
//udp.EnableBroadcast = true; //This was suggested in a now deleted answer
IPEndPoint groupEP = new IPEndPoint(IPAddress.Broadcast, port);
string str4 = "I want to receive this!";
byte[] sendBytes4 = Encoding.ASCII.GetBytes(str4);
udp.Send(sendBytes4, sendBytes4.Length, groupEP);
udp.Close();
However, it's kind of useless if I can't then receive it on another computer. All I need is to send a command to another computer on the LAN, and for it to receive it and do something.
Without using a Pcap library, is there any way I can accomplish this? The computer my program is communicating with is Windows XP 32-bit, and the sending computer is Windows 7 64-bit, if it makes a difference. I've looked into various net send commands, but I can't figure them out.
I also have access to the computer (the XP one)'s local IP, by being able to physically type 'ipconfig' on it.
EDIT: Here's the Receive function I'm using, copied from somewhere:
public void ReceiveBroadcast(int port)
{
Debug.WriteLine("Trying to receive...");
UdpClient client = null;
try
{
client = new UdpClient(port);
}
catch (Exception ex)
{
Debug.WriteLine(ex.Message);
}
IPEndPoint server = new IPEndPoint(IPAddress.Broadcast, port);
byte[] packet = client.Receive(ref server);
Debug.WriteLine(Encoding.ASCII.GetString(packet));
}
I'm calling ReceiveBroadcast(15000) but there's no output at all.
Here is the simple version of Server and Client to send/receive UDP packets
Server
IPEndPoint ServerEndPoint= new IPEndPoint(IPAddress.Any,9050);
Socket WinSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
WinSocket.Bind(ServerEndPoint);
Console.Write("Waiting for client");
IPEndPoint sender = new IPEndPoint(IPAddress.Any, 0)
EndPoint Remote = (EndPoint)(sender);
int recv = WinSocket.ReceiveFrom(data, ref Remote);
Console.WriteLine("Message received from {0}:", Remote.ToString());
Console.WriteLine(Encoding.ASCII.GetString(data, 0, recv));
Client
IPEndPoint RemoteEndPoint= new IPEndPoint(
IPAddress.Parse("ServerHostName"), 9050);
Socket server = new Socket(AddressFamily.InterNetwork,
SocketType.Dgram, ProtocolType.Udp);
string welcome = "Hello, are you there?";
data = Encoding.ASCII.GetBytes(welcome);
server.SendTo(data, data.Length, SocketFlags.None, RemoteEndPoint);
I try to send a string over the network, this is my code:
IPEndPoint serverEndPoint = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 25);
TcpClient client = new TcpClient(serverEndPoint);
Socket socket = client.Client;
byte[] data = Encoding.ASCII.GetBytes(response);
socket.Send(data, data.Length, SocketFlags.None);
socket.Close();
client.Close();
When I run it I got System.Net.Sockets.SocketException
If you are using a connectionless protocol, you must call Connect before calling Send, or Send will throw a SocketException. If you are using a connection-oriented protocol, you must either use Connect to establish a remote host connection, or use Accept to accept an incoming connection.
Refer Socket.Send Method (Byte[], Int32, SocketFlags)
Assuming you are using a connectionless protocol the code should be like this,
string response = "Hello";
IPAddress ipAddress = IPAddress.Parse("127.0.0.1");
if (ipAddress != null)
{
IPEndPoint serverEndPoint = new IPEndPoint(ipAddress, 25);
byte[] receiveBuffer = new byte[100];
try
{
using (TcpClient client = new TcpClient(serverEndPoint))
{
using (Socket socket = client.Client)
{
socket.Connect(serverEndPoint);
byte[] data = Encoding.ASCII.GetBytes(response);
socket.Send(data, data.Length, SocketFlags.None);
socket.Receive(receiveBuffer);
Console.WriteLine(Encoding.ASCII.GetString(receiveBuffer));
}
}
}
catch (SocketException socketException)
{
Console.WriteLine("Socket Exception : ", socketException.Message);
throw;
}
}
Next time, try including the exception message to explain what actually went wrong.
Am trying to make a simple UDP application using C sharp,nothing sophisticated,connect,send some text,and receive it! but it keeps throwing this exception!
"An existing connection was forcibly closed by the remote host"!
The code :
byte[] data = new byte[1024];
IPEndPoint ipep = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 9050);
Socket server = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
string welcome = "Hello, are you there?";
data = Encoding.ASCII.GetBytes(welcome);
server.SendTo(data, data.Length, SocketFlags.None, ipep);
IPEndPoint sender = new IPEndPoint(IPAddress.Any, 0);
EndPoint tmpRemote = (EndPoint)sender;
data = new byte[1024];
int recv = server.ReceiveFrom(data, ref tmpRemote);
Console.WriteLine("Message received from {0}:", tmpRemote.ToString());
Console.WriteLine(Encoding.ASCII.GetString(data, 0, recv));
Console.WriteLine("Stopping client");
server.Close();
thanks =)
You should tell the system that you are listening for UDP packets on port 9050 before you call Receive.
Add server.Bind(ipep); after Socket server = new Socket(...);
Have you tried checking that the IP address is valid and the port is not being used for something else?
Windows:
Start > Run > "cmd" > "ipconfig".
Try turning off your firewall software.
If you do not know the IP of the answering server, you better do:
recv = server.Receive(data);
Here is my suggetion to your code. You can use a do-while loop using a condition (in my example it is an infinite loop):
byte[] data = new byte[1024];
IPEndPoint ipep = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 9050);
Socket server = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
string welcome = "Hello, are you there?";
data = Encoding.ASCII.GetBytes(welcome);
server.ReceiveTimeout = 10000; //1second timeout
int rslt = server.SendTo(data, data.Length, SocketFlags.None, ipep);
data = new byte[1024];
int recv = 0;
do
{
try
{
Console.WriteLine("Start time: " + DateTime.Now.ToString());
recv = server.Receive(data); //the code will be stoped hier untill the time out is passed
}
catch { }
} while (true); //carefoul! infinite loop!
Console.WriteLine(Encoding.ASCII.GetString(data, 0, recv));
Console.WriteLine("Stopping client");
server.Close();
Here is my code
Socket sck = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
sck.Bind(new IPEndPoint(IPAddress.Any, 0));
// Broadcast to find server
string msg = "Imlookingforaserver:" + udp_listen_port;
byte[] sendBytes4 = Encoding.ASCII.GetBytes(msg);
IPEndPoint groupEP = new IPEndPoint(IPAddress.Parse("255.255.255.255"), server_port);
sck.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.Broadcast, 1);
sck.SendTo(sendBytes4, groupEP);
//Wait response from server
Socket sck2 = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
sck2.Bind(new IPEndPoint(IPAddress.Any, udp_listen_port));
byte[] buffer = new byte[128];
EndPoint remoteEndPoint = new IPEndPoint(IPAddress.Any, udp_listen_port);
sck2.ReceiveFrom(buffer, ref remoteEndPoint); //<<< I never pass this line
I use above code to try find a server. First I broadcast a message and then I wait for a response from the server.
A test I made with the server written in C++ and running in Windows Vista, client written in C# and run on the same machine with server.
Problem is: The server can receive message which client broadcast, but client can not receive anything from server.
I try to write a client with C++ and it work like a charm, I think my problem is in C# client.
I would start listening on that port before you broadcast. You're using UDP which is connectionless so you could be missing your packet.
Socket sck = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
sck.Bind(new IPEndPoint(IPAddress.Any, 0));
//Wait response from server
Socket sck2 = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
sck2.Bind(new IPEndPoint(IPAddress.Any, udp_listen_port));
byte[] buffer = new byte[128];
EndPoint remoteEndPoint = new IPEndPoint(IPAddress.Any, udp_listen_port);
// Broadcast to find server
string msg = "Imlookingforaserver:" + udp_listen_port;
byte[] sendBytes4 = Encoding.ASCII.GetBytes(msg);
IPEndPoint groupEP = new IPEndPoint(IPAddress.Parse("255.255.255.255"), server_port);
sck.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.Broadcast, 1);
sck.SendTo(sendBytes4, groupEP);
sck2.ReceiveFrom(buffer, ref remoteEndPoint);