To configure alternative ports to listen in apache, modify the apache configuration directives as below,
=-=-=-
Listen *:808
NameVirtualHost *:808
VirtualHost *:808
ServerName domain.com
DocumentRoot /www/a
/VirtualHost
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Now the domain can be accesed via a.foo.com:808
=-=-=-
Listen *:808
NameVirtualHost *:808
VirtualHost *:808
ServerName domain.com
DocumentRoot /www/a
/VirtualHost
=-=-=-=-
Now the domain can be accesed via a.foo.com:808