FAQ commonly

Q. 80/443 port is already binded. Who are using that ports?
A. In case of Windows, you can find him through below steps.
To find the process ID using 80 port on Prompt window.
> netstat -o -n -a | findstr 0.0:80
TCP 0.0.0:80 LISTENING 21120
To find the process name.
> tasklist /FI "PID eq 21120"

Image Name                    PID  Session Name       Session#  Memory Usage
========================= ======== ================ =========== ============
Skype.exe                     4624 Console                    1    219,292 K

In case of Linux, you can find it below command.

netstat -tulpn | grep :80

To find the process name.
> ls -l /proc/31787/exe

lrwxrwxrwx. 1 imptt imptt 0 Feb  2 11:11 /proc/31787/exe -> /usr/java/jdk1.8.0_40/jre/bin/java

Q. Memory usage is high. Is there problem?
In case of Linux, if memmory is cached. it would be no problem.

top - 02:03:34 up 210 days, 15:42,  1 user,  load average: 0.00, 0.00, 0.00
Tasks: 150 total,   1 running, 149 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:   8022288k total,  7638412k used,   383876k free,     8940k buffers
Swap:  4112376k total,        0k used,  4112376k free,    547016k cached

On upper case, you can find 547016k is cached.
If you want to decrease it forcely, you can use below command.(CentOS, redhat)

> sync
> sysctl -w vm.drop_caches=3
> sysctl -w vm.drop_caches=0

Actually you need to check the free mamory with below.
> free -m
CentOS 6.x: check the free of "-/+ buffers/cache".
CentOS 7.x: check the available.

Q. Too many file opens?
In Linux system, the max opened file count is 1024, You need to increase of that.
Please refer to https://stackoverflow.com/questions/20901518/ubuntu-too-many-open-files
You can check problem by using below commands

How many are files opened?
ls -l /proc/{ptt server's process id}/fd/ | wc -l

What is limitation of ptt server about max files?
cat /proc/{ptt server's process id}/limits

What is detail of opened files?
lsof -p {ptt server's process id}