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 | ||
| --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 | |
| --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
