Udp receive problem

[Daniel Lindberg]

Hi, im a beginner in C# and i just cant seem to get my udp broadcasting to
work. What happens is that it just locks down on the Receive call and never
gets any data.
I have the code for the server who answers the broadcast, so i know that it
sends a reply, but i cant figure out why my C# client cant receive it..

Any input on whats wrong with my code will be appreciated


//My code...
byte[] buffer = new byte[50];

Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram,
ProtocolType.Udp);

socket.Bind(new IPEndPoint(IPAddress.Any, 0));

socket.Connect(new IPEndPoint(IPAddress.Broadcast, 4242));

socket.Send(System.Text.ASCIIEncoding.ASCII.GetBytes((char)2+"0"+(char)9+"1"
+(char)3));

socket.Receive(buffer, 0, 50, SocketFlags.None);

textBox1.Text = Encoding.ASCII.GetString(buffer);

 

[Tom Spink]

Hi, im a beginner in C# and i just cant seem to get my udp broadcasting to
work. What happens is that it just locks down on the Receive call and
never gets any data.
I have the code for the server who answers the broadcast, so i know that
it sends a reply, but i cant figure out why my C# client cant receive it..

Any input on whats wrong with my code will be appreciated


//My code...
byte[] buffer = new byte[50];

Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram,
ProtocolType.Udp);

socket.Bind(new IPEndPoint(IPAddress.Any, 0));

socket.Connect(new IPEndPoint(IPAddress.Broadcast, 4242));

socket.Send(System.Text.ASCIIEncoding.ASCII.GetBytes((char)2+"0"+(char 9+"1"
+(char)3));

socket.Receive(buffer, 0, 50, SocketFlags.None);

textBox1.Text = Encoding.ASCII.GetString(buffer);

Hi Daniel,

For UDP Broadcasting, you should be using the SendTo and ReceiveFrom
methods. You also shouldn't be connecting to anything.

The ReceiveFrom method takes an IPEndPoint as a ref parameter, which should
be initialised as:

EndPoint remoteEndPoint = new IPEndPoint( IPAddress.Broadcast, 4242 );

Then, call socket.ReceiveFrom using 'ref remoteEndPoint' as the parameter.
The remoteEndPoint object will also be modified to point to the endpoint
that the broadcast message originated from.

Here's a short example:

///
public void BroadcastTest ( )
{
// Instantiate
Socket sck = new Socket( AddressFamily.InterNetwork,
SocketType.Dgram,
ProtocolType.Udp );

// Bind
sck.Bind( new IPEndPoint( IPAddress.Any, 0 ) );

// Broadcast ABCD
sck.SendTo( new byte[] { 0x41, 0x42, 0x43, 0x44 },
new IPEndPoint( IPAddress.Broadcast, 4242 ) );

// Receive on the broadcast IP, port 4242
EndPoint remoteEndPoint = new IPEndPoint( IPAddress.Broadcast, 4242 );

byte[] recvBuffer = new byte[128];
int bytesReceived = sck.ReceiveFrom( recvBuffer, ref remoteEndPoint );
}
///

Note: I typed this straight into KNode, I haven't tested it in the
slightest... but it just so happens that I've been coding some UDP
broadcast stuff lately, so this is fresh in my memory.

 

[Daniel Lindberg]

I had to add this row before the sendto command:
sck.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.Broadcast,1);

But after that it worked like a charm. Thank you for your help!

Hi, im a beginner in C# and i just cant seem to get my udp broadcasting to
work. What happens is that it just locks down on the Receive call and
never gets any data.
I have the code for the server who answers the broadcast, so i know that
it sends a reply, but i cant figure out why my C# client cant receive it..

Any input on whats wrong with my code will be appreciated


//My code...
byte[] buffer = new byte[50];

Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram,
ProtocolType.Udp);

socket.Bind(new IPEndPoint(IPAddress.Any, 0));

socket.Connect(new IPEndPoint(IPAddress.Broadcast, 4242));

socket.Send(System.Text.ASCIIEncoding.ASCII.GetBytes((char)2+"0"+(char 9+"1"
+(char)3));

socket.Receive(buffer, 0, 50, SocketFlags.None);

textBox1.Text = Encoding.ASCII.GetString(buffer);

Hi Daniel,

For UDP Broadcasting, you should be using the SendTo and ReceiveFrom
methods. You also shouldn't be connecting to anything.

The ReceiveFrom method takes an IPEndPoint as a ref parameter, which should
be initialised as:

EndPoint remoteEndPoint = new IPEndPoint( IPAddress.Broadcast, 4242 );

Then, call socket.ReceiveFrom using 'ref remoteEndPoint' as the parameter.
The remoteEndPoint object will also be modified to point to the endpoint
that the broadcast message originated from.

Here's a short example:

///
public void BroadcastTest ( )
{
// Instantiate
Socket sck = new Socket( AddressFamily.InterNetwork,
SocketType.Dgram,
ProtocolType.Udp );

// Bind
sck.Bind( new IPEndPoint( IPAddress.Any, 0 ) );

// Broadcast ABCD
sck.SendTo( new byte[] { 0x41, 0x42, 0x43, 0x44 },
new IPEndPoint( IPAddress.Broadcast, 4242 ) );

// Receive on the broadcast IP, port 4242
EndPoint remoteEndPoint = new IPEndPoint( IPAddress.Broadcast, 4242 );

byte[] recvBuffer = new byte[128];
int bytesReceived = sck.ReceiveFrom( recvBuffer, ref remoteEndPoint );
}
///

Note: I typed this straight into KNode, I haven't tested it in the
slightest... but it just so happens that I've been coding some UDP
broadcast stuff lately, so this is fresh in my memory.