I have a Raspberry Pi 3 with Raspbian installed on it. However, I've tried also tried Ubuntu Mate, and I had the same problem. After a while my LAMP server, SSH server and FTP server become unreachable. I tried to see if it was a problem with the connection, but the ICMP protocol worked perfectly. Does anyone have any advice?
EDIT: this morning worked well for about an hour before the problem.
lsof -i tcp:80
for a normal HTTP server should show apache/httpd there. If not the server has gone down. If it is there something strange is perhaps going on with DNS. Clarify the context by explaining where the server is in relation to the clients: Are they all on a home LAN? If so, how does the server get an IP and how is the hostname resolution taking place? Avahi? – goldilocks♦ Aug 29 '16 at 14:36