Document revision date: 19 July 1999 | |
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The UseNet protocol describes how to store and send groups of messages between computers that may or may not be on the Internet. UseNet (the User's Network) is a virtual forum divided into newsgroups that deal with various topics. The site administrator who sets up a newsgroup determines the topic of the newsgroup. Internet newsgroups are similar to notes conferences; they provide vast amounts of information.
You can use a UseNet reader software program to access a newsgroup. Discussions are conducted by sending e-mail messages to the newsgroup's address. If the newsgroup is moderated, the moderator screens the mail before posting it to the newsgroup.
A news reader, mxrn, is available on the Freeware CD.
TCP/IP networking applications support general user operations that access resources, such as files. One method of controlling who can access operating system resources is by assigning identification codes to users.
Both OpenVMS based systems and UNIX-based systems use identification codes as a general method of resource protection. However, each of the operating systems implement the coding differently. Because the TCP/IP software was originally developed on and used for UNIX machines, TCP/IP implementations use UNIX-style identification codes. Consequently, some TCP/IP applications must map UNIX identification codes to OpenVMS identification codes.
This chapter includes summary information about OpenVMS and UNIX
identification codes and the mapping mechanisms used by TCP/IP
applications.
4.1 What Are UIDs and GIDs?
OpenVMS users are familiar with the OpenVMS user identification code (UIC) that identifies the user as a member of a group that can share specific data. The UIC corresponds to the name of the user who created the process running on OpenVMS. The UIC is a 32-bit field comprising a 14-bit user number and a 14-bit group number. UIC-based protection controls access to such objects as files and directories.
Just as OpenVMS employs user names and UICs for identification, UNIX identifies users by user names and a user identification (UID) group identification (GID) pair. Both UIDs and GIDs are simply numbers that can identify a user on a system. Some versions of UNIX (for example, Digital UNIX) use 32-bit UID/GID pairs.
Some TCP/IP applications require use of UID/GID pairs for user
identification. The most common application that requires this
identification is the NFS (Network File System) client/server
application. To use this application on OpenVMS, you must map OpenVMS
user names to UNIX-style GID/UID pairs.
4.2 Establishing the Relationship Between UID/GID Pairs and OpenVMS User Names
All TCP/IP vendors for OpenVMS support mechanisms for mapping OpenVMS user names to UID/GID pairs. Consult the appropriate vendor documentation for more information about how to manage this process for a particular OpenVMS TCP/IP layered product. (Appendix A lists TCP/IP layered products that run on OpenVMS.)
OpenVMS users can use familiar DCL commands, with special parameters and qualifiers, to log in, connect to a remote host over a TCP/IP connection, copy or transfer files from host to host, and display remote host directories on the local host. The local host and any remote hosts involved in these operations must be running one of the TCP/IP layered software products provided by one of the vendors listed in Appendix A.
This chapter describes the the COPY, DIRECTORY, and SET HOST DCL
commands and their special parameters and qualifiers that support
TCP/IP networking.
5.1 Remote Terminal Services
If you are a user on an OpenVMS client system running TCP/IP software, you can use SET HOST commands to access virtual terminal services, including:
This section presents the formats of the SET HOST commands supported over TCP/IP connections:
The SET HOST commands invoke the RLOGIN and TELNET client programs. A
remote host is identified either by its Internet Protocol (IP) host
name or by its IP address (see Chapter 2). See Section 3.2 for a
description of the TCP/IP client/server applications that supply remote
terminal services.
5.1.1 Kerberos Authentication
Kerberos authentication is a system that verifies the identity of users, thereby providing security in a network environment that otherwise may not be secure. Some TCP/IP software products use Kerberos to make sure the identity of any user who requests access to a remote host is authentic.
Kerberos keeps a control list of users and their encrypted passwords. Users must obtain Kerberos tickets to invoke utilities that support commands with special Kerberos enhancements. RCP, RLOGIN, and TELNET applications can support Kerberos enhancements.
When a TCP/IP layered product supports Kerberos authentication, a user on an OpenVMS system can specify the /AUTHENTICATE qualifier in any of the following OpenVMS DCL commands:
The DCL commands SET HOST/RLOGIN and COPY/RCP support the following three distinct case-sensitive forms of the /USERNAME qualifier value. Enclose the user name in quotes to preserve its case.
$ set host/rlogin/username=ralf host.dom |
$ set host/rlogin/username="RaLf" host.dom |
$ set host/rlogin/username="RALF" host.dom |
This command logs the user in to a remote host over a TCP/IP connection and starts an interactive terminal session by accessing the RLOGIN application.
SET HOST/RLOGIN
DCL> SET HOST/RLOGIN REMOTEHST1 |
This command connects you to a remote host over a TCP/IP connection by invoking the TELNET application.
SET HOST/TELNET
DCL> SET HOST/TELNET remotehst2 |
This command connects your local host to a remote IBM host over a TCP/IP connection and invokes the TN3270 terminal emulator TELNET client program.
SET HOST/TN3270
DCL> SET HOST/TN3270 REMOTEHST3 |
OpenVMS DCL commands support file manipulation utilities over TCP/IP connections, including:
The file access applications require a utility at the local terminal
and one or more remote servers. See Section 3.3 for a description of
remote file access utilities supported by TCP/IP.
5.2.1 File Length and File Format
The majority of files copied are ASCII text or binary images. These files are handled properly by all TCP/IP vendors' RCP or FTP applications. TCP/IP was written for UNIX systems, which use 512-byte blocks. OpenVMS, however, uses Record Management Services (RMS) as the native file system. RMS handles variable-length records and multiple file formats. Copying a file with any kind of record-oriented format to a UNIX system causes the file attributes to be lost.
Some of the TCP/IP products that run on OpenVMS (as described in
Appendix A), allow copying of an FDL (file definition language) file
so that OpenVMS can restore RMS file attributes retrieval. Most TCP/IP
products on OpenVMS support special copying modes that preserve file
attributes when files are copied to or from OpenVMS systems.
5.2.2 Remote File Specification Format
You can use OpenVMS DCL commands to access remote files over TCP/IP connections simply by including in the file specification the name of the remote host on which the file is located. You can access files that are protected against general access if the owner has provided you with the name and password of the account.
The OpenVMS DCL commands for TCP/IP support the same remote file specification format as the DCL commands for DECnet network connections. Some implementations of the file transaction applications support file transfers in which both the source file and the destination file are remote file specifications.
The full format for a remote file specification is as follows:
host"username password account"::remote-file-spec |
If a file resides on a system other OpenVMS, enclose the name of the file in quotation marks. For example, to access a file named /usr/users/user/Orders on a Digital UNIX host named U32, you would use the following format for the file specification:
U32"user password"::"/usr/users/user/Orders" |
Unlike OpenVMS, UNIX systems support case-sensitive file specifications.
(See also Section 5.1.2 for a description of case-sensitive user names.)
5.2.3 COPY/FTP
This command transfers files between hosts, that possibly have
dissimilar file systems, over a TCP/IP connection by invoking the FTP
utility.
COPY/FTP from-file to-file |
In OpenVMS to OpenVMS transfers, if both machines support VMS structured transfers, the /BINARY, /ASCII, and /FDL qualifiers are ignored. The cooperating OpenVMS FTP client and server automatically transfer the file with proper OpenVMS attributes. |
DCL> COPY/FTP/ASCII/ANON ovms_file1.c remotehst5::"/public/ovms_file2.c" |
DCL> COPY/FTP/FDL/ANON rms_indexed_file.idx remotehst5::"/public/rms.idx.file" |
This command copies files from host to host over a TCP/IP connection by invoking the RCP utility.
COPY/RCP from-file to-file |
DCL> COPY/RCP local_file.c remotehst4"Smith smpw"::rem_file.c |
FTP applications support commands to manage the directory to or from
which you are transferring files. The DCL command DIR/FTP gets a list
of the contents of the remote directory. Section 3.3.2 describes how to
use FTP in listing remote directories.
5.3.1 DIR/FTP
This command displays remote directory information over a TCP/IP connection by invoking the FTP utility.
DIR/FTP directory-spec |
DCL> DIR/FTP remotehst6"Jones jpw"::"usr/public" |
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