Are you tired of being clueless about your network connections and traffic on your Linux system? The good news is that there’s a powerful command line tool called netstat that can help you monitor and manage network connections, ports, and protocols. In this blog post, we’ll explore the essential usage of the netstat command to diagnose networking issues or optimize performance on Linux. Whether you’re a beginner or an experienced user, read on to learn how to become a netstat ninja!
Established Connection
netstat is a versatile command-line utility that can be used to get information about network connections and devices.
One use of netstat is to determine which services are using the most bandwidth. Use the -a option to display all active network connections, including both listening and connected sockets. For example:
netstat -a | grep LISTEN
This will output a list of all active sockets, including both listening and connected instances of protocols like TCP and UDP. You can also use netstat to monitor traffic on individual ports:
netstat -p tcp |grep 22
This will display all traffic on port 22 on your system.
Listening Connection
Listening on interface: lo
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 127.0.0.1:5353 127.0.0.1:* LISTEN 8887/sshd tcp6 0 0 :::22 [::1]:3333 ESTABLISHED 18558/ncurses
Port Number used by PID
The netstat command is used to display active sockets, routing table information, and interface statistics on a Linux server. The port number used by PID can be displayed using the following command:
netstat -p tcp | grep “PID”
If the PID is not listed in the output, then the port number is not being used by that process.
All Protocols Statistics
When troubleshooting network problems, Linux users might want to check the status of protocol connections with the netstat command.
The netstat command provides a variety of information on network connections, including the number of packets transmitted and received, open files, and ports in use. Table 1 shows the most common options for netstat.
Table 1: Common Options for the Netstat Command
Option Description -a Shows all active protocols. -b Shows only activeopen ports. -c Shows CONNECT statistics only. -d Shows DIR statistics only. -e Shows both active and passive modes of open ports. -p Shows only active processes. This is equivalent to -o all except that it does not list listening sockets or UNIX domain sockets (SOCK_STREAM). -s Shows SYN_RCVD, SYN_SENT, and FIN_RCVD statistics for each connected socket. If no arguments are given, netstat displays statistics for all interfaces on the system. Note that some options require root privileges; see man 6 stat for more information.
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Kernel routing information
The netstat command is a versatile tool that can be used to examine the network connections and configurations of a Linux system. One of the most common uses for netstat is to view information on the routing tables.
To view the routing table information using netstat, use the following syntax:
netstat -r
The -r option displays all routing entries in the table. The following example shows how to display the routing table information for a Linux system:
# netstat -r Routing Table — 2 entries ———————————————————— gateway = 10.10.10.1 local_port = 3000 (eth0) remote_port = 3306 (wlan0) proto = udp dpt : 3000 -> 10.10.10.2 : icmp type = 0 code : udp dpt : 3306 -> 10.10.10.1 : icmp type = 1 code : icmp
PID used by Port Number
The pid (process identification number) is a unique identifier for each process on a system. It can be used with the netstat command to get information about the current processes on your machine.
To use the netstat command, open a terminal and type:
netstat –p
This will display all of the active processes on your machine. The first column will show the PID of the process, and subsequent columns will list information about the process, such as its name, CPU utilization, memory usage, and network connections.
To see information about a specific process, type:
netstat –p | grep
List of network interfaces
There are three main ways to use the netstat command on Linux.
The first way is to use it as a tool for viewing active network connections. This can be done by issuing the following command:
netstat -an
This will show you all of the active network connections on your system.
The second way to use netstat is to use it as a tool for viewing passive network connections. This can be done by issuing the following command:
netstat -pp
This will show you all of the passive network connections on your system.
Finally, netstat can also be used as a tool for viewing routing information. This can be done by issuing the following command:
Continuous Listening
Continuous listening is the process of monitoring network traffic on a regular basis in order to determine potential security threats or issues. This can be done by using the netstat command on Linux. It provides general information about network connections and their status, as well as information about active packets and bytes transmitted and received.
The netstat command can be used to display active TCP connections, active UDP connections, active ICMP messages, and open files. Additionally, it can be used to display the list of processes that are currently using any given port. This is helpful in determining which applications or services may be causing traffic issues.
To use the netstat command, first open a terminal window by typing “terminal” into your favorite search engine or application menu. Once you have opened the terminal window, type “netstat” followed by a space and then press Enter. This will start the netstat command in interactive mode. You can then use the arrow keys to select the items you want to view from the list that appears onscreen. For example, if you wanted to see information about active TCP connections, you would press Ctrl + A (or Cmd + A on Mac) after entering “netstat”.
When you have finished viewing the information displayed by the netstat command, type “exit” followed by a space and then press Enter to exit out of it.
Conclusion
In this article, we have looked at the netstat command and its usage. We learned about different options and how to use it to get information on network activity. Finally, we summarized all the important points in this article with a few tips. In conclusion, netstat is a very useful tool for monitoring network traffic and performance on a Linux system.
