The TCPGUI interface is the part of LISTSERV that listens for TCP/IP connections coming into the LISTSERV port on the LISTSERV host. To use the TCPGUI interface, you set up TCPGUI, then you send commands to it through TCP/IP. You have two options for sending commands to LISTSERV through TCP/IP:
If it needs to be restricted to a given IP address, or if port 2306 is already in use by another application, LISTSERV must be set up so that it listens to the correct IP address and port.
The lcmdx program (C language code at the end of the chapter) allows you to send a LISTSERV command from a command line (DOS, shell, or DCL prompt). Compile and link it (you may need to make minor changes to get it to compile, depending on your C compiler) to produce an executable.
Note: Under Solaris, most network programs require you to pass the ‘
-lsocket -lnsl’ flags to the compiler when compiling. If this is not done, then compiling LCMDX.C under Solaris will fail with network-related library errors.
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hostname is the DNS name of the LISTSERV host,
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command is the one-line LISTSERV command.
Note: The password parameter MUST imperatively be typed in UPPER CASE.
For example, if francoise@lsoft.com wants to set her subscription to the MSVC list to digest, and her password on PEACH.EASE.LSOFT.COM (where this list is hosted) is "ABCDE", she can use the following command:
Any one-line command can be submitted to LISTSERV in this way. To use lcmdx directly from your application, just spawn a subprocess or send the lcmdx command using whatever means is provided by the operating system under which your application is running.
The lcmdx program is convenient, as it doesn't require programming to use, but it does not allow much flexibility in how your application can react to LISTSERV's responses to the commands sent. For greater flexibility, you can integrate the techniques used in lcmdx for communicating with LISTSERV directly into your application.
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receive - used by LSV_send_command to receive a string of a given length from a socket
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LSV_send_command - the function that sends a command from LISTSERV and returns the answer; this function can be used directly by your application with few or no changes.
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main - the main function simply parses the command line for lcmdx into its component parts, passes them to LSV_send_command, and prints LISTSERV's response; your application would replace main.
The main change that you may want to make to the LSV_send_command function, will be to have it write the LISTSERV response to a string or an array of strings rather than to a file, as is the case in lcmdx. What you actually do with LISTSERV's response will be dictated by the needs of your application.
The only other changes that might be required are changes that relate to how sockets are implemented on your operating system. For example, if you are using Windows sockets (WINSOCK), you would have to add the Windows sockets initialization code at the start of your application, calling and checking the status of the WSAStartup routine; and the cleanup code at the end, calling the routine WSACleanup. With Windows sockets, you would also have to include the header file <winsock.h> instead of <sys/socket.h>, <netdb.h>, and <netinet/in.h>; and replace the call to close(ss) with a call to closesocket(ss).
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hostname - a pointer to a character array containing the name of the LISTSERV host to which to send the command
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port - the port number to which to connect (use 2306 unless otherwise specified in the site configuration file of the LISTSERV host)
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origin - a pointer to a character array containing the e-mail address of the "originator" of the command
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pw - a pointer to a character array containing the LISTSERV password registered for the originator's e-mail address (must be UPPER CASE)
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command - a pointer to a character array containing the one-line command to send to LISTSERV
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writeto - a pointer to the file in which to write LISTSERV's response; as mentioned above, depending on the needs of your application, you may want to change this parameter and the code within LSV_send_command that writes to this file.
Of course, if you use LSV_send_command without modification, you will be opening and closing a connection to LISTSERV for each command you send. You can make your application more efficient by opening up a connection to LISTSERV and sending a series of commands before closing the connection again. The LSV_send_command function will work "out of the box", but an experienced programmer can use it as a guide for developing customized functions for working with the TCPGUI interface.
The technique described above, using the LSV_send_command function to send commands over TCP/IP to LISTSERV, will work for most one-line LISTSERV commands, such as ADD, DELETE, SET, SHOW, etc. However, some commands require a different or modified approach:
Multi-line commands cannot be sent through the TCPGUI interface, therefore the usual approach for sending a list header to LISTSERV (the PUT command followed by the multiple lines of the header) cannot be used. Instead, TCPGUI has a special command for sending a list header: X-STL.
where header-data is a text string that contains every header line (including the leading asterisk), one after the other, each preceded by a count of the characters on the line, followed by an underscore character. The last header line should not have any trailing spaces.
Note: If double quotes are required (for instance, for the Prime= or Sender= keyword settings), you MUST escape them with a backslash character, thus:
(remember that the entire command must be on one line, not wrapped as is unavoidable in this document). Additionally, when counting characters for the line counts, the backslash-double quote combination counts as a single character. If the line count is wrong, you will get an "Error in header data stream" error.
The LSV_send_command function generally requires a password, which you don’t necessarily have when you’re in the process of adding one. In this case, you can send the command anonymously through TCPGUI by using the anonymous e-mail address "@" as the "originator" in the call to LSV_send_command (but not in the X-PWADD command, obviously).
When LISTSERV receives the X-PWADD command, it sends e-mail to the given e-mail-address requesting confirmation. E-mail confirmation is the only way for LISTSERV to determine that the e-mail address provided is truly the correct address. Therefore, an application should never count on the password being immediately available. A message to the user, letting them know that they can continue after they have successfully confirmed the password registration, may be advisable.
As noted above, the TCPGUI interface can only handle single-line commands. Therefore bulk operations, such as the bulk add and delete commands cannot be sent through TCPGUI, and can only be sent through the mail. The only ways to send bulk adds and deletes from an application are:
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Open up a connection with the SMTP port on the LISTSERV host and use SMTP commands (documented in RFC821) to send a mail file (documented in RFC822) containing the bulk add or delete job. This is essentially the same thing as the previous bullet, except that in the latter case, you used a third-party application to send the file, whereas with this method you must write your own.
LISTSERV will accept almost any one-line command through the TCPGUI interface. The answer you receive through the TCPGUI interface, however, may not always be what you expected. Commands whose responses tend to be long will generally be sent through e-mail. LISTSERV will always send the response to the following commands back through e-mail:
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REVIEW – requires the "MSG" option
Some commands that can be sent through the TCPGUI interface and to which LISTSERV will send the response back through the TCPGUI interface nevertheless have responses that are human-friendly but not application-friendly. One such command is the QUERY command, which sends a response that looks like:
***SUBDATE*** date***TOPICS*** subscriber-topics
***TOPLIST*** list-topics
***HDR*** e-mail-address (next subscriber)
etc.
If this command is sent using an address that is subscribed to the given list, it works exactly the same as the "QUERY ***GUI***" command described above. If it is sent anonymously (see "Adding or replacing a password" above) or from an address which is not subscribed, then the first line in the response is:
***MBX*** user1@host.domainFirstname Lastname <user1@host.domain>
***MBX*** user2@host2.domain
"Full name w/ special characters" <user2@host2.domain>
etc.
***END***
SCAN: N matches.
When the command you send produces an error the TCPGUI interface sends back the exact error that you would receive through the mail when that error is detected by LISTSERV (for example, if you use the wrong listname, or misspell a command). However, the TCPGUI interface does have some error messages specific to it, for when the error occurs within TCPGUI rather than LISTSERV. These are:
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