TCP/IP ports range from 1 to 65535. Abyss Web Server reports a listening problem on a port when one of the following situations is happening:
Another instance of Abyss Web Server is already running on your computer.
The user has not the privilege to use the port: Due to the operating system policy, only the applications launched by the super-user root can use ports ranging from 1 to 1023. If you run Abyss Web Server as a normal user, you cannot use any port below 1024.
The port is already used by another application: Try stopping the other applications running on your computer to know which one is already using this port. More specifically, port 80 is usually used by other web servers. So if Abyss Web Server cannot listen to this port, there are chances that another web server is already running.
An alternative solution would be to configure Abyss Web Server to use another web server or console port. For more information about changing the web server port, refer to "General server configuration".
If you have to change the console port, choose a temporary console port number and invoke Abyss Web Server using ./abyssws -p <temporary console port>. Open the console and go to Console Port in Console Configuration, change the console port and restart the server. See "Changing the console port" for more help.