To stream, DaCast needs ports 80, 443 or 1935 open to stream. The service checks first on 1935 when streaming. Most setups should have these ports already opened by default.
To find this, you can use the Command Prompt. Please search for how to use the command prompt for your particular version of windows, although most (like Windows 7 and 8) just require you to search cmd.
Once there, type in "netstat -a" in the Command Prompt window, and press Enter.
This will give you a result like below:
Any ports stating as "LISTENING" mean they are open. In the example above, both ports 80 and 443 are open.