The SocketTools Library Edition includes libraries that
implement fourteen standard Internet application protocols, as well
as libraries which provide support for general TCP/IP networking
services, encoding and compressing files, processing e-mail
messages and ANSI terminal emulation. The following libraries are
included in the SocketTools Library Edition:
Domain Name Service Library
The Domain Name Service (DNS) protocol is what applications use to
resolve domain names into Internet addresses, as well as provide
other information about a domain, such as the name of the mail
servers which are responsible for receiving e-mail for users in
that domain. The DNS library enables an application to query one or
more nameservers directly, without depending on the configuration
of the client system.
File Encoding Library
The File Encoding library provides functions for encoding and
decoding binary files, typically attachments to e-mail messages.
The process of encoding converts the contents of a binary file to
printable text. Decoding reverses the process, converting a
previously encoded text file back into a binary file. The library
supports a number of different encoding methods, including support
for the base64, uucode, quoted-printable and yEnc algorithms. The
library can also be used to compress and expand data in a
user-supplied buffer or in a file.
File Transfer Protocol Library
The File Transfer Protocol (FTP) library provides functions for
uploading and downloading files from a remote host, as well as a
variety of remote file management functions. In addition to file
transfers, an application can create, rename and delete files and
directories, list files and search for files using wildcards. The
library provides both high level functions, such as the ability to
transfer multiple files in a single function call, as well as
access to lower level remote file I/O functions.
Finger Protocol Library
The Finger protocol is used to return information about a user on a
remote server, as well as general information about the server
itself. The library provides an interface for connecting to a
server, requesting information about a user and returning that
information to the program. Unlike some other protocols, where you
can connect once and then perform any number of operations, the
Finger protocol requires that you establish a new connection for
each request that is made.
Gopher Protocol Library
The Gopher protocol is a document retrieval protocol that pre-dates
the Hypertext Transfer Protocol. The advantage that Gopher offers
is that it is a simpler, lightweight protocol that doesn’t have the
inherent overhead and complexity of a typical HTTP server. It is
most commonly used with internal corporate networks to provide
access to documents, although its use is less common today than it
was several years ago. The SocketTools library provides a complete
interface to the Gopher protocol. It includes the ability to list
and select documents, as well as enabling a program to retrieve the
contents of a document for processing or storage on the local
system.
Hypertext Transfer Protocol
Library
The Hypertext Transfer Protocol (HTTP) library provides an
interface for accessing documents and other types of files on a
server. In some ways it is similar to the File Transfer Protocol in
that it can be used to upload and download files; however, the
protocol has expanded to also support remote file management,
script execution and distributed authoring over the World Wide Web.
The SocketTools Hypertext Transfer Protocol library implements
version 0.9, 1.0 and 1.1 of the protocol, including features such
as support for proxy servers, persistent connections, user-defined
header fields and chunked data.
Internet Control Message Protocol
Library
The Internet Control Message Protocol (ICMP) is commonly used to
determine if a remote host is reachable and how packets of data are
routed to that system. Users are most familiar with this protocol
as it is implemented in the ping and tracert command line
utilities. The ping command is used to check if a system is
reachable and the amount of time that it takes for a packet of data
to make a round trip from the local system, to the remote host and
then back again. The tracert command is used to trace the route
that a packet of data takes from the local system to the remote
host, and can be used to identify potential problems with overall
throughput and latency. The library can be used to build in this
type of functionality in your own applications, giving you the
ability to send and receive ICMP echo datagrams in order to perform
your own analysis.
Internet Message Access Protocol
Library
The Internet Message Access Protocol (IMAP) is an application
protocol which is used to access a user’s e-mail messages which are
stored on a mail server. However, unlike the Post Office Protocol
(POP) where messages are downloaded and processed on the local
system, the messages on an IMAP server are retained on the server
and processed remotely. This is ideal for users who need access to
a centralized store of messages or have limited bandwidth. For
example, traveling salesmen who have notebook computers or mobile
users on a wireless network would be ideal candidates for using
IMAP. The SocketTools IMAP library implements the current standard
for this protocol, and provides functions to retrieve messages, or
just certain parts of a message, create and manage mailboxes,
search for specific messages based on certain criteria and so on.
The API is designed as a superset of the Post Office Protocol API,
so developers who are used to working with the POP3 library will
find the IMAP library very easy to integrate into an existing
application.
Mail Message Library
The Mail Message library provides an interface for composing and
processing e-mail messages and newsgroup articles which are
structured according to the Multipurpose Internet Mail Extensions
(MIME) standard. Using this library, an application can easily
create complex messages which include multiple alternative content
types, such as plain text and styled HTML text, file attachments
and customized headers. It is not required that the developer
understand the complex MIME standard; a single function call can be
used to create multipart message, complete with a styled HTML text
body and support for international character sets. The Mail Message
library can be easily integrated with the other mail related
protocol libraries, making it extremely easy to create and process
MIME formatted messages.
Network News Transfer Protocol
Library
The Network News Transfer Protocol (NNTP) is used with servers that
provide news services. This is similar in functionality to bulletin
boards or message boards, where topics are organized hierarchically
into groups, called newsgroups. Users can browse and search for
messages, called news articles, which have been posted by other
users. On many servers, they can also post their own articles which
can be read by others. The largest collection of public newsgroups
available is called USENET, a world-wide distributed discussion
system. In addition, there are a large number of smaller news
servers. For example, Microsoft operates a news server which
functions as a forum for technical questions and announcements. The
SocketTools library provides a comprehensive interface for
accessing newsgroups, retrieving articles and posting new articles.
In combination with the Mail Message library to process the news
articles, SocketTools can be used to integrate newsgroup access
with an existing e-mail application, or you can implement your own
full-featured newsgroup client.
Post Office Protocol Library
The Post Office Protocol (POP) provides access to a user’s new
e-mail messages on a mail server. Functions are provided for
listing available messages and then retrieving those messages,
storing them either in files or in memory. Once a user’s messages
have been downloaded to the local system, they are typically
removed from the server. This is the most popular e-mail protocol
used by Internet Service Providers (ISPs) and the SocketTools
library provides a complete interface for managing a user’s
mailbox. This library is typically used in conjunction with the
Mail Message library, which is used to process the messages that
are retrieved from the server.
Remote Command Protocol Library
The Remote Command protocol is used to execute a command on a
server and return the output of that command to the client. The
SocketTools library provides an interface to this protocol,
enabling applications to remotely execute a command and process the
output. This is most commonly used with UNIX based servers,
although there are implementations of remote command servers for
the Windows operating system. The SocketTools library supports both
the rcmd and rshell remote execution protocols and provides
functions which can be used to search the data stream for specific
sequences of characters. This makes it extremely easy to write
Windows applications which serve as light-weight client interfaces
to commands being executed on a UNIX server or another Windows
system. The library can also be used to establish a remote terminal
session using the rlogin protocol, which is similar to how the
Telnet protocol functions.
Secure Shell Protocol Library
The Secure Shell (SSH) protocol is used to establish a secure
connection with a server which provides a virtual terminal session
for a user. Its functionality is similar to how character based
consoles and serial terminals work, enabling a user to login to the
server, execute commands and interact with applications running on
the remote host. The SSH library provides an API for establishing
the connection and handling the standard I/O functions needed by
the program. The library also provides functions that enable a
program to easily scan the data stream for specific sequences of
characters, making it very simple to write light-weight client
interfaces to applications running on the server.
Simple Mail Transfer Protocol
Library
The Simple Mail Transfer Protocol (SMTP) enables applications to
deliver e-mail messages to one or more recipients. The library
provides an API for addressing and delivering messages, and
extended features such as user authentication and delivery status
notification. Unlike Microsoft’s Messaging API (MAPI) or
Collaboration Data Objects (CDO), there is no requirement to have
certain third-party e-mail applications installed or specific types
of servers installed on the local system. The SocketTools library
can be used to deliver mail through a wide variety of systems, from
standard UNIX based mail servers to Windows systems running
Exchange or Lotus Notes and Domino. Using the SocketTools library,
messages can be delivered directly to the recipient, or they can be
routed through a relay server, such as an Internet Service
Provider’s mail system. The Mail Message library can be integrated
with this library in order to provide an extremely simple, yet
flexible interface for composing and delivering mail messages.
SocketWrench Library
The SocketWrench library provides a higher-level interface to the
Windows Sockets API, designed to be suitable for programming
languages other than C and C++. If needed, function calls can be
intermixed between the SocketWrench and Windows Sockets libraries.
In addition, the Secure Edition supports secure communications
using the Secure Sockets Layer (SSL) and Transport Layer Security
(TLS) protocols. Note that in order to access the secure features
in SocketWrench, a Secure Edition development license is
required.
Telnet Protocol Library
The Telnet protocol is used to establish a connection with a server
which provides a virtual terminal session for a user. Its
functionality is similar to how character based consoles and serial
terminals work, enabling a user to login to the server, execute
commands and interact with applications running on the remote host.
The Telnet library provides an API for establishing the connection,
negotiating certain options (such as whether characters will be
echoed back to the client) and handling the standard I/O functions
needed by the program. The library also provides functions that
enable a program to easily scan the data stream for specific
sequences of characters, making it very simple to write
light-weight client interfaces to applications running on the
server. This library can be combined with the Terminal Emulation
library to provide complete terminal emulation services for a
standard ANSI or DEC-VT220 terminal.
Terminal Emulation Library
The Terminal Emulation library provides a comprehensive API for
emulating an ANSI or DEC-VT220 character terminal, with full
support for all standard escape and control sequences, color
mapping and other advanced features. The library functions provide
both a high level interface for parsing escape sequences and
updating a display, as well as lower level primitives for directly
managing the virtual display, such as controlling the individual
display cells, moving the cursor position and specifying display
attributes. This library can be used in conjunction with the Remote
Command or Telnet Protocol library to provide terminal emulation
services for an application, or it can be used independently. For
example, this library could also be used to provide emulation
services for a program that provides serial modem connections to a
server.
Time Protocol Library
The Time Protocol library provides an interface for synchronizing
the local system’s time and date with that of a remote server. The
library enables developers to query a server for the current time
and then update the system clock if desired.
Whois Protocol Library
The Whois protocol library provides an interface for requesting
information about an Internet domain name. When a domain name is
registered, the organization that registers the domain must provide
certain contact information along with technical information such
as the primary name servers for that domain. The Whois protocol
enables an application to query a server which provides that
registration information. The SocketTools library provides an API
for requesting that information and returning it to the program so
that it can be displayed or processed.