To monitor an Internet server you'll first need to define a new Sentry. To open the Sentry Configuration dialog box, choose Create New from the Sentry section of the Object Manager, or choose Add Sentry from the Setup pull-down menu. Select the type of server you want to monitor by selecting one of the six server-type buttons at the top of the Sentry Configuration window. You may define up to 10 Sentries in PageSentry, or 100 Sentries in PageSentry Pro. You can have each Sentry monitor a different Internet service running on a single server, one service running on different servers, or any combination of the two. The following section describes the various input fields and configuration options for the different types of Internet servers that Page Sentry is capable of monitoring.

Common Elements

Each type of Sentry is configured in two parts. The upper half of the Configuration screen details how each individual Sentry is configured and the bottom half of the screen is used to select and deselect Notifiers to be triggered when a Sentry encounters an error. We'll talk about the Notifiers in detail in the section entitled "Defining Notifiers". Each Sentry uses a slightly different combination of input fields in the top half of the Configuration screen, but they all include the following fields:

Sentry Name

This is the name that will be reported in an e-mail message or AppleEvent notification. You can name a Sentry anything you like, since it has no effect on the server check, but each Sentry must have a unique name. Also, you should choose a name that you will be able to easily recognize when the Sentry notifies you of a problem, such as "Primary Web Server" or "E-mail Server".

Log File

The Log File is where a particular Sentry will store a record of its activities. This filename can be the same as other Sentries, or you can have each Sentry log to a different file. To log entries to a new log file, just type the name of the new log file in the Log File field and it will be created automatically. Leaving this field blank prevents PageSentry from logging anything for this Sentry.

Frequency

The Frequency setting, anywhere from one minute to one week, will determine how often PageSentry will test the page. Pulse Sentries have a frequency range of 10 minutes to 30 days. Checking your server more than once a minute is probably overkill since the test performed for a single check may in some cases take more than a minute.

Note that a single request does not usually require a great deal of processing by a server, so there is little performance penalty in having PageSentry check your server fairly often. In general, having PageSentry check the page every 3 to 10 minutes will give you timely notification without imposing a noticeable load on your server.

Each Sentry type except the "Pulse" also has an "Execute Test" button that lets you immediately run the test defined for the Sentry. The ability to run Sentry tests immediately gives you an easy way to verify that you have created the Sentry correctly.

For FTP Sentries, running the test also automatically fills in the checksum and length fields, saving you from having to compute these manually. Executing the test of a DNS Sentry will autmoatically populate the IP Address field, if it has not yet been entered.

In addition to these common fields, each Sentry will need more information relating to the type of server being monitored. The additional configuration information required for each type of Sentry is explained below.

HTTP

PageSentry is capable of monitoring any type of Web server (Macintosh, UNIX, Windows NT, etc.) by requesting a URL and examining the returned document. This includes HTML text, CGIs, and clickable image maps. Figure 5 shows the HTTP Sentry Configuration dialog box.

To configure the Sentry just fill in the appropriate fields. In addition to the common configuration options, the HTTP Sentry has the following options:

Check URL

This is the URL that the Sentry will use to retrieve a page from your Web server. The format should be something like this: "http://www.yourcom.com/file.html." You can omit the filename and simply get the default page from the server or include a CGI name. As with any Web browser, you can retrieve graphics or binary data files just by entering the appropriate URL. You can also add a port number after the domain name to monitor servers running on non-standard ports. For example, "http://www.yourcom.com:8000/" would cause PageSentry to test the server on port 8000, instead of the default port 80.

Verify Phrase

This is an optional field for which a Sentry can search in the page returned from the server. If you specify a string (two or more characters) here and the Sentry cannot find this string in the retrieved page, the Sentry will fail and run its Notifiers (described below). For example, you can check that a Web page contains the string "</HTML>" to make sure that the whole file was retrieved by a Sentry. String comparisons are not case sensitive.

It is best to specify a verify phrase that is unique to the requested page. For example, "</HTML>" is a good default, since it appears in most Web pages, but will also appear in most cases when the requested file can't be found and an error file is sent to the browser. Setting the verify phrase to a unique string in the requested page will tell you that not only is the server returning Web pages, but that they are the correct Web pages.

Note that the verify phrase can also appear in the HTTP header, as well as in the HTML page returned. This allows you to test non-text files by setting the verify phrase to a string that will appear in the HTTP header, such as "GIF" for GIF image files.

Username and Password

The Username and Password fields can be used to test Web pages that are protected by basic authentication by Web server realms or products like WebLock.

SMTP

Most Internet e-mail servers use the Simple Mail Transfer Protocol (SMTP) to transmit e-mail from server to server, including the Apple Internet Mail Server (AIMS). PageSentry monitors this type of server by sending an SMTP command to the server as if it were an e-mail client or another server verifying the existence of a user. By verifying the username, PageSentry effectively tests the SMTP server's mail database without generating unnecessary mail messages.

To configure the Sentry just fill in the appropriate fields. In addition to the common configuration options, the SMTP Sentry has the following options:

Server Address

This is the domain name or IP number of the SMTP server you want to test. This is usually something like "mail.yourcom.com"or simply "yourcom.com." You can specify a non-standard TCP port number by appending a colon and the port number to the server address (e.g., :8001). The default port is 25.

Username:

Enter the name of a valid e-mail account on the server in the Username field; PageSentry will ask the server if this user exists. Most mail servers generally have "root" or "postmaster"defined, even if the SMTP server is only used to forward outgoing mail. You can also simply use your own mail account name, assuming you have an account on the server you are testing.

FTP

PageSentry uses a URL to locate a file on an FTP server, verify that it exists, and check it's data. When this Sentry runs, it downloads the file, computes a checksum, and records the length of the file for later comparison.

In addition to the common configuration options, the FTP Sentry has the following options:

Retrieve File

This is the URL of the file to get via FTP. It needs to be a complete URL as in "ftp://ftp.yourcom.com/file.hqx." You can specify a non-standard TCP port number by appending a colon (":") and the number to the machine name. The default port is 21.

Username and Password:

A Sentry uses information in these fields when logging into an FTP server. Most servers will have "anonymous" defined and will want your e-mail address as the password. You must complete these fields.

Checksum and Length

You cannot edit these fields, but they act much like the "Verify Phrase" field in the HTTP Sentry. When the file is retrieved from the FTP server, the Sentry will compare the checksum and the length of the new file with those values stored in these fields. This ensures that the file is the same and has not been corrupted. You can click on the "Execute Test" button to retrieve the file immediately and display these values. If you do not click the "Execute Test" button before clicking "OK,"the Sentry will store the values from the first retrieval the Sentry performs. If the length is different or the checksum doesn't match, the Sentry will "fail" and run the appropriate Notifier.

Telnet

Most UNIX computers and terminal servers are capable of running a Telnet daemon (pronounced dee-mon), which allows remote users to login to perform tasks and issue commands. In addition, many modern networking devices such as hubs, routers, and bridges can also host limited Telnet capabilities that allow for remote management and administration. However, since PageSentry can't download and examine a file for a particular phrase, checksum, or length PageSentry looks for a word or phrase during the login procedure as a means of verifying the server's availability.

To configure the Sentry, just fill in the appropriate fields. In addition to the common configuration options, the Telnet Sentry has the following options:

Machine Name

The Machine Name is the IP name or address of the UNIX computer, terminal server, or networking device you want to test. You can specify a non-standard TCP port number by appending a colon and the number to the machine name (e.g., :8001). The default port is 23.

Verify Phrase

The "Verify Phrase" field is the text that PageSentry checks for in the greeting text sent by the Telnet server when a connection is opened. Use your favorite Telnet client (such as NCSA Telnet) to connect and see this message.

Common phrases will be "login:" or "password:."Many servers also send a line with the name and version of the operating system they are running, like "SunOS UNIX."You can leave this field blank and PageSentry will only test whether or not a connection can be made. String comparisons are not case sensitive.

DNS

The DNS Sentry acts as a low-level resolver and connects directly to the target Domain Name System server to perform a query. This means that the test is completely independent of the host files, DNR cache, or resolver code on the PageSentry Macintosh, whether running Open Transport or MacTCP.

To configure the Sentry just fill in the appropriate fields. In addition to the common configuration options, the DNS Sentry has the following options:

DNS Address

This is the domain name or IP number of the machine running the DNS server that you wish to monitor. The Sentry will connect to TCP port 53 (the default) to perform the query. Using a domain name in the DNS Address field requires that the domain name be resolved before the Domain Name Server can be tested, creating ambiguity in testing. It is best to enter the IP address of your Domain Name Server, as opposed to the domain name, so that the test will always report the correct error in the event of a DNS failure.

Domain Name

This is the domain name the Sentry will try to resolve into an IP number. You can check the intranet ability of the name server by asking it to resolve a machine name within the domain for which it is authoritative (like yourmachine.yourcompany.com). Or, you can check its Internet ability by asking it to resolve an external machine name (like www.foreign.com). If you choose domain names that can resolve to multiple IP addresses (like www.apple.com or www.microsoft.com), different answers will be returned to PageSentry each time it tries to resolve that domain name. In this case, use the "*" option in the IP Address field, described below.

IP Address

This is the IP number that will be compared with the address returned from the DNS being tested. You can use the Execute Now button to have PageSentry fill in this field, or you can fill it in the expected IP number yourself.

In some cases, domain names can resolve to more than one IP Address, as is the case with "Round Robin" Web sites. For this reason, you can enter an asterisk ("*") in the IP Address field, which tells PageSentry that any valid response from the Domain Name Server is acceptable. TCP/IP problems and Errors sent by the DNS will still be reported by PageSentry, but in this case PageSentry will not verify the exact IP Address returned.

Pulses

A unique feature of PageSentry is its ability to monitor itself using a "Pulse." To ensure reliability, PageSentry will check in with you periodically via e-mail or an AppleEvent-aware application to let you know that PageSentry is "on the job."The final link in the chain of server monitoring, however, is you: If you don't hear from PageSentry on schedule, then something has gone wrong with the PageSentry Mac, the network connection, or the notification application (if you're using an AppleEvent-driven application in a Notifier).

To configure the Pulse just fill in the appropriate fields. In addition to the common configuration options, the Pulse Sentry has the following options:

Scheduled At

This fields specifies the "anchor time" PageSentry uses to synchronize the pulse. For example, if you have a pulse Frequency of 6 hours and an anchor time of midnight, as in the above example, the Sentry will only run at midnight, 6 AM, noon, and 6 PM. It won't care when you last rebooted or launched PageSentry; it will run at those times, and only then. This is different from other Sentries, which would run 6 hours after PageSentry was launched. The Pulse can be sent as low as every 10 minutes and as high as one month, which is also different from the other types of Sentries.

Status Report

This field determines what is reported by the Pulse to the e-mail or AppleEvent notification. You may choose to have the Pulse Sentry send nothing, a simple one-line status report, or a detailed multiple-line status report. This field effects the report sent via mail or AppleEvent, not the option selected in the Logging Preferences, which determines what is written to the local disk in the log files.