Networking is an essential part Unix and it offer lots of tools and command to diagnose any networking problem. When I was working on FIX Protocol we get lot of support queries to see whether FIX Sessions
are connected or not. Since FIX Protocol uses sockets you can use net
stat , telnet and other networking command available in Linux for
finding problem and solve that.In this article I will show you basic networking commands in Unix and for what purpose they are used. with the combination of grep and find command on them you can troubleshoot most of networking problem
hostname
hostname with no options displays the machines host name
hostname –ddisplays the domain name the machine belongs to
hostname –fdisplays the fully qualified host and domain name
hostname –idisplays the IP address for the current machine
ping
It sends packets of information to the user-defined source. If the packets are received, the destination device sends packets back. Ping can be used for two purposes
1. To ensure that a network connection can be established.
2. Timing information as to the speed of the connection.
If you do ping www.yahoo.com it will display its IP address. Use ctrl+C to stop the test.
ifconfig
View network configuration, it displays the current network adapter configuration. It is handy to determine if you are getting transmit (TX) or receive (RX) errors.
netstat
Most useful and very versatile for finding connection to and from the host. You can find out all the multicast groups (network) subscribed by this host by issuing "netstat -g"
netstat -nap | grep portwill display process id of application which is using that port
netstat -a or netstat –allwill display all connections including TCP and UDP
netstat --tcp or netstat –twill display only TCP connection
netstat --udp or netstat –uwill display only UDP connection
netstat -gwill display all multicast network subscribed by this host.
nslookup
If you know the IP address it will display hostname. To find all the IP addresses for a given domain name, the command nslookup is used. You must have a connection to the internet for this utility to be useful.
E.g. nslookup blogger.com
You can also use nslookup to convert hostname to IP Address and from IP Address from hostname.
traceroute
A handy utility to view the number of hops and response time to get to a remote system or web site is traceroute. Again you need an internet connection to make use of this tool.
finger
View user information, displays a user’s login name, real name, terminal name and write status. this is pretty old unix command and rarely used now days.
telnet
Connects destination host via telnet protocol, if telnet connection establish on any port means connectivity between two hosts is working fine.
telnet hostname port will telnet hostname with the port specified. Normally it is used to see whether host is alive and network connection is fine or not.
Networking Commands Example in Unix and Linux
These are most useful commands in my list while working on Linux server , this enables you to quickly troubleshoot connection issues e.g. whether other system is connected or not , whether other host is responding or not and while working for FIX connectivity for advanced trading system this tools saves quite a lot of time- finding host/domain name and IP address - hostname
• test network connection – ping
• getting network configuration – ifconfig
• Network connections, routing tables, interface statistics – netstat
• query DNS lookup name – nslookup
• communicate with other hostname – telnet
• outing steps that packets take to get to network host – traceroute
• view user information – finger
• checking status of destination host - telnet
Example of Networking commands in Unix
let's see some example of various networking command in Unix and Linux. Some of them are quite basic e.g. ping and telnet and some are more powerful e.g. nslookup and netstat. When you used these commands in combination of find and grep you can get anything you are looking for e.g. hostname, connection end points, connection status etc.hostname
hostname with no options displays the machines host name
hostname –ddisplays the domain name the machine belongs to
hostname –fdisplays the fully qualified host and domain name
hostname –idisplays the IP address for the current machine
ping
It sends packets of information to the user-defined source. If the packets are received, the destination device sends packets back. Ping can be used for two purposes
1. To ensure that a network connection can be established.
2. Timing information as to the speed of the connection.
If you do ping www.yahoo.com it will display its IP address. Use ctrl+C to stop the test.
ifconfig
View network configuration, it displays the current network adapter configuration. It is handy to determine if you are getting transmit (TX) or receive (RX) errors.
netstat
Most useful and very versatile for finding connection to and from the host. You can find out all the multicast groups (network) subscribed by this host by issuing "netstat -g"
netstat -nap | grep portwill display process id of application which is using that port
netstat -a or netstat –allwill display all connections including TCP and UDP
netstat --tcp or netstat –twill display only TCP connection
netstat --udp or netstat –uwill display only UDP connection
netstat -gwill display all multicast network subscribed by this host.
nslookup
If you know the IP address it will display hostname. To find all the IP addresses for a given domain name, the command nslookup is used. You must have a connection to the internet for this utility to be useful.
E.g. nslookup blogger.com
You can also use nslookup to convert hostname to IP Address and from IP Address from hostname.
traceroute
A handy utility to view the number of hops and response time to get to a remote system or web site is traceroute. Again you need an internet connection to make use of this tool.
finger
View user information, displays a user’s login name, real name, terminal name and write status. this is pretty old unix command and rarely used now days.
telnet
Connects destination host via telnet protocol, if telnet connection establish on any port means connectivity between two hosts is working fine.
telnet hostname port will telnet hostname with the port specified. Normally it is used to see whether host is alive and network connection is fine or not.
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