Q. What is a port?

A port is software docking point in your machine where remote application uses for communication. This is analogy to the physical ports for entering in to the Countries.

Q. What is hardware port?

This is physical peripheral connection point to a machine from a physical device.

Q. What is a socket?

Socket is mix of software Port+IP address.

Q. What is the range of ports or how many ports are there?

Port numbers can vary from 0 to 65535, so total we can get 65536 ports

Q. Why port numbers are just 65536?

This is because limitation in TCP/IP stack where the port field is just 16bit size. So we get only 2^16 port which is equal to 65536 ports

Q.What are the well-known ports?

Well known ports are from 0 to 1023(total 2^10=1024 ports)

Q.What do you mean by default port?

Default port is a designated port for particular well-known server.

Q.Can we change default port for a service(example Apache, squid)?

Yes, we can change

Q.What are the protocol numbers for TCP and UDP?

TCP protocol number:6

UDP protocol number:17

Databases
3306	MySQL
1433	MS SQL Server
5432	PostgreSQL
Remote Access - Graphical
3389	MS Remote Desktop
5800	VNC-HTTP
5900	VNC
Remote Access - Console
22	SSH
23	Telnet
512	Rexec
513	Rlogin
514	RSH
Remote Data Transfer & Management
20	FTP Data
21	FTP
69	TFTP
2049	NFS
Directory Service
389	LDAP
636	LDAP Secure
Web
80	HTTP
443	HTTPS
3128	Squid Web Proxy
Mail & Chat
25	SMTP
110	POP3
995	POP3S
143	IMAP
993	IMAPS
5222	Jabber
5223	Jabber SSL
Infrastructure Management
53	DNS
1512	WINS
67	DHCP Server
68	DHCP Client
123/UDP	NTP
161	SNMP

Easy Steps to Nginx Installation

Follow these Steps Blindly !

1. yum install svn pcre-devel openssl-devel zlib

2. cd /usr/local/src

3. wget http://nginx.org/download/nginx-1.4.1.tar.gz
4. svn checkout http://nginx-upstream-jvm-route.googlecode.com/svn/trunk/ nginx-upstream-jvm-route-read-only
5. tar -xzvf nginx..tar.gz

6. cd nginx.

7. patch -p0 < /path/to/nginx-upstream-jvm-route-read-only/jvm_route.patch

8. ./configure --prefix=/etc/nginx --sbin-path=/usr/sbin/nginx --conf-path=/etc/nginx/nginx.conf --error-log-path=/var/log/nginx/error.log --http-log-path=/var/log/nginx/access.log --pid-path=/var/run/nginx.pid --lock-path=/var/run/nginx.lock --user=nginx --group=nginx --with-http_ssl_module --with-http_realip_module --with-http_sub_module --with-http_gzip_static_module --with-http_stub_status_module --with-http_gzip_static_module --with-http_ssl_module --with-debug --add-module=/usr/local/src/nginx-upstream-jvm-route-read-only/

9. make

10. make install


11. save this file to "/etc/init.d/nginx"
http://wiki.nginx.org/RedHatNginxInitScript

12. chmod ug+x /etc/init.d/nginx