![]() For this reason, you should regularly check the ports opened by your system. Moreover, there is a possibility that a Trojan that is already in your system may install a so-called backdoor and open a corresponding port in the process. The big problem with these open ports is the fact that they offer third parties the opportunity to sneak malware into your system. These connections are established via the respective network address, which indicates, among other things, which port was opened in advance for data exchange. ![]() Tcp 0 0 rhel.test:56598 about the incoming and outgoing connections of your computer or server gives you a big advantage in the fight against disproportionate traffic and malicious software. Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name To do so, use the following command: ~]# netstat -tpĪctive Internet connections (w/o servers) If all of this filtered data isn't for you, consider pulling the raw stats: ~]# netstat -statistics -rawĪ really handy trick for troubleshooting is to list out a service by PID. ![]() To pull and view network statistics sorted by protocol use the following: ~]$ netstat -sĩ TCP sockets finished time wait in fast timerġ delayed acks further delayed because of locked socketģ8 acknowledgments not containing data payload receivedġ connections reset due to early user closeįilters can be implemented for specific protocols in the same way that the connections/ports were filtered. Now that we know how to view connections and listening ports, let's take a look at pulling statistics. For this example, we will use http: ~]# netstat -ap | grep http We run the standard netstat -ap and then pipe to grep for a search key. The combination of netstat and grep are very commonly used for finding the number of listening programs on a port. You can apply filters to the listening ports as well by adding the -t and -u options depending on your desired protocol. Unix 2 STREAM LISTENING 14186 this output was edited for length. To list all actively listening ports (both TCP and UDP), use the following command: ~]$ netstat -lĪctive Internet connections (only servers)Īctive UNIX domain sockets (only servers) The same filter can be used to pull UDP connections down. This gives you a much more user-friendly readout of the TCP connections only. If you found the -a option to be too verbose, try the -t flag with it: ~]$ netstat -at ![]() If this looks like a lot of information to you, that is because it is a lot of information! Unix 2 STREAM LISTENING 14186 2 STREAM LISTENING 41653 2 STREAM LISTENING 41742 this output was edited for length. Unix 2 STREAM LISTENING 41743 /tmp/.ICE-unix/2613 Unix 2 STREAM LISTENING 38125 /tmp/.ICE-unix/2276 Unix 2 STREAM LISTENING 38124 2 STREAM LISTENING 41812 /tmp/.X11-unix/X0 Proto RefCnt Flags Type State I-Node Path Tcp 0 0 rhel.test:49608 :http TIME_WAITĪctive UNIX domain sockets (servers and established) Tcp 0 0 rhel.test:domain 0.0.0.0:* LISTEN Proto Recv-Q Send-Q Local Address Foreign Address State To list all listening ports, using both TCP and UDP, use netstat -a: ~]$ netstat -aĪctive Internet connections (servers and established) Let's take a look at some of the basic usage for netstat and the most used cases. Both incoming and outgoing connections, routing tables, port listening, and usage statistics are common uses for this command. The network statistics ( netstat) command is a networking tool used for troubleshooting and configuration, that can also serve as a monitoring tool for connections over the network. Linux system administration skills assessment.A guide to installing applications on Linux.Download RHEL 9 at no charge through the Red Hat Developer program.
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