Check plugins - check-tcp

check-tcp is a plug-in that monitors connections to servers via TCP.

Configurable options

Option	Short	Description	Default value
--service		Specify a service name. see [Supported services](#Supported services)
--hostname	-H	Host name or IP address to check for communication
--port	-p	Port number to check for communication
--send	-s	String to be sent to server
--expect-pattern	-e	Regular expression patterns expected in responses from the server
--quit	-q	String to be sent when disconnecting from the server
--ssl	-S	TLS connection required or not	false
--unix-sock	-U	Unix socket
--no-check-certificate		Whether or not certificate verification is required	false
--status-as		Overwrite the monitoring status. For Example, If you specify UNKNOWN=CRITICAL, the monitoring status will become CRITICAL when it is UNKNOWN. Multiple values can be specified, separated by commas.
--timeout	-t	Connection timeout time (sec)	10
--maxbytes	-m	Disconnects when more than the specified number of bytes of data is received
--delay	-d	Latency between sending data and polling for a response (sec)
--warning	-w	Response time as Warning (sec)
--critical	-c	Response time as Critical (sec)
--escape	-E	Escape if the string specified by --quit contains \n \r \t \c. If not specified, add \r\n at the end of the string specified by --quit.	false
--error-warning	-W	Set the alert status to WARNING when the plugin terminates abnormally	CRITICAL
--expect-closed	-C	Verify that the port/unixsock is closed. If the port/unixsock is closed, OK status returned; if open, Critical or Warning status is returned depending on the value of the --error-warning. This option only verifies the connection.	false

Supported services

If you specify the corresponding service name in the --service option, the check will be performed for each corresponding option.

Service name	port	send	expect-pattern	quit	ssl
FTP	21		^220	QUIT
POP	110		^\+OK	QUIT
SPOP	995		^\+OK	QUIT	✓
IMAP	143		^\* OK	a1 LOGOUT
SIMAP	993		^\* OK	a1 LOGOUT	✓
SMTP	25		^220	QUIT
SSMTP	465		^220	QUIT	✓
GEARMAN	7003	version\n	\A[0-9]+\.[0-9]+\n\z

Example configuration

The following is a configuration that checks for connections on port 4224 of localhost, and if the connection takes more than 3 seconds, it is set to Warning, and if it takes more than 5 seconds, it is set to Critical.

[plugin.checks.check-tcp-sample]
command = ["check-tcp", "-H", "localhost", "-p", "4224", "-w", "3", "-c", "5"]

To verify the above settings by executing directly from a terminal or other means, execute as follows.

check-tcp -H localhost -p 4224 -w 3 -c 5

To specify an IPv6 address, enclose it in single-byte brackets [] like [::1].

[plugin.checks.check-tcp-v6-sample]
command = ["check-tcp", "-H", "[::1]", "-p", "4224", "-w", "3", "-c", "5"]

Tips

The check-tcp plugin can check the correctness of simple message exchanges during connection checking.

The --service option checks messages according to the supported protocols, but you can also use --send or --expect-pattern to monitor your own protocols.

For example, to check that the reason phrase in the HTTP response status line is the expected message, the following configuration can be used.

[plugin.checks.tcp_http404]
command = ["check-tcp", "-H", "localhost", "-p", "80", "-s", "GET / HTTP/1.1\\r\\n\\r\\n", "-e", "HTTP/1.1 404 Bad Request", "-E"]

To check the operation in advance, perform the following.

check-tcp -H localhost -p 80 -s "GET / HTTP/1.1\r\n\r\n" -e "HTTP/1.1 404 Bad Request" -E

Repository

https://github.com/mackerelio/go-check-plugins/tree/master/check-tcp