C function for sending ASCII text as UDP packet

Posted on 2009-04-10
Last Modified: 2012-05-06
I'm trying to write a C function that accepts an ASCII string as it's input parameter and broadcasts that text over the network as a UDP packet.

I have no idea where to start with this.

Here's a brief example of what i mean...
int main( int argc, const char* argv[] )
void SendTextViaUdpBroadcast ( TextIn )
	// Here the contents of TextIn are send as ascii in a udp packet as a broadcast (to ip

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Question by:davepusey
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Expert Comment

ID: 24116882
You want to set the EnableBroadcast property on the UdpClient instance
set to true. Once you do that, you want to send your request to the IP
address of From the documentation for the EnableBroadcast
property on the UdpClient class:
Broadcasting is limited to a specific subnet. You can broadcast to your
local subnet by sending a packet to; or, you can use the
directed broadcast address, which is the network portion of an Internet
Protocol (IP) address with all bits set in the host portion. For example, if
your IP address is (a Class C address, with the network portion
as the first three octets, and the host portion is the last octet), your
directed broadcast address is

Expert Comment

ID: 24116911
This manual will be a great help for you!!

Author Comment

ID: 24116970
Maybe i should clarify... This is C on linux (debian/ubuntu).

How do i open the socket in the first place?

How do i send the packet?

How do i close the socket afterwards?

Accepted Solution

ewest02 earned 500 total points
ID: 24124642

   fd = socket()      // create a socket
   sendto( fd, ...)            // send datagram to listening socket
   recvfrom( fd, ...)        // get response from server
   close( fd)           // close the socket

An excellent text for the fine details is  Stevens, Unix Network Programming
A quick overview can be had with

Author Comment

ID: 24132995
I'd already figured it out by the time you'd posted, but i'll give you the points anyway seeing as it's what i came up with.

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