Ssh is a common port for connecting remote linux servers, and this port is also the default port number. When making a remote connection, please enter the correct port number in the port location, otherwise the connection will not succeed. View that port value in the default configuration file.
Use lsof to check the open ports of the current system. Whether you log in directly to the system or connect through ssh, you can use the lsof command to check the port: this command is used to find files and processes used by users.
First, connect the linux host and enter the linux command line state waiting for input instructions. At the command line, enter the command: lsof-I: 22, and then press Enter. At this point, the open status of all ssh ports will be printed.
How to view the firewall open port of Linux system?
Iptables is the CentOSX version of the packet filtering firewall program. To check whether the IPTABLES firewall is started by using "serviceiptablesstatus", to start the iptables firewall by using "serviceiptablesstart", to stop, change the start to stop, and to restart, change the start to restart.
Nmap Tool Detecting Open Ports nmap is a tool for network scanning and host detection. The installation of nmap is very simple, as shown in the rpm installation below. With regard to the use of nmap, you can write a close-up by growing up, so I won't expand it here.
Windowsserver's operating system should open the port in the firewall, and linux operating system should add the configuration information of the open port in iptables.
What command can I use under linux to see which ports iptables has opened?
1, iptables is the CentOSX version of the packet filtering firewall program. To check whether the IPTABLES firewall is started, use "serviceiptablesstatus", and to start the iptables firewall, use "serviceiptablesstart", change start to stop, and change start to restart.
2. In Linux system, you can use the sudoiptables command to open the port. Here is a simple example. Suppose we want to open port 8080 to all network access: first, log in to Linux system.
3. It seems that there are two main ways to open ports under ubuntu. One is ubuntu's own firewall, and the other is iptables. We mainly use iptables here. In general, iptables will be installed when ubuntu is installed, and there is no problem. You can install it with a command.
4.iptables-a output-ptcp-dport port number -jDROP Open port number: iptables-a input-ptcp-dport port number -jACCEPT The following is how to use the linux open port command.
Linux view runs port commands.
Query the specified port through grep filtering: netstat-tnlp | grep: 80 Use ss to check whether the port ss is a new netstat, and the command options are basically the same. It lacks some functions of netstat, but it exposes more TCP state and is a little faster.
Linux view port number command provides you with graphic information of Linux view port number command. Open the linux system and right-click on the blank space of the linux desktop. In the drop-down options that pop up, click Open Terminal. Enter the command cat/etc/services in the terminal window, and then enter the view server port.
Further use the command: ps-aux|grepjava, or directly: ps-aux|greppid to check, you can clearly know which program port 8080 is occupied! Then judge whether to use the KILL command to kill! This is what Linux should learn. Learn more commands.
Introduction to the lsof command The lsof command is used to display a list of all files currently open in the Linux system. Looking at the files opened by the process or system will bring great help to debugging. Here is a brief introduction to the commonly used functions of lsof.
Many friends want to know how linux checks the port opening. Let's have a look! Open the linux viewing port to open the linux system, and right-click on the blank space of the linux desktop. In the drop-down options that pop up, click Open Terminal.
Lsof-I: port, using lsof-I: port, you can see the programs running at the specified port and the current connection.