I am not shure if a certain port is open on the system. I need to know which ports are opened.
You can use the lsof command to check your opened ports. lsof -i (this shows all your opened ports) lsof -i :25 (this give you an answer for the smtp port on your system)
About the Author
Wim Peeters is electronics engineer with an additional master in IT and over 30 years of experience including time spent in support, development, consulting, training and database administration. Wim has worked with SQL Server since version 6.5. He has developed in C/C++, Java and C# on Windows and Linux in different European countries and different European languages. He writes knowledge base articles to solve IT problems and publishes them on the Lubby Knowledge Platform where he is one of the most important contributors and the main developer.