TCP/IP Libraries

This chapter contains descriptions of the TCP/IP library functions, data structures, and protocols, all arranged in alphabetical order.

We've also provided summary lists of all the entries:

• arranged alphabetically by name
• arranged by category

There's also a discussion of what you'll find in a function description.

Alphabetical list of entries

Entries by category

In this chapter, you'll notice that many functions are related to other functions. This section arranges the functions into the following categories:

• Current host
• Data server
• Host database
• Internet address manipulation
• Miscellaneous
• Network database
• Network protocol database
• Network services database
• Protocols
• Remote hosts
• Resolver
• SNMP messages
• Sockets
• Socket messages
• SOCKS server
• Virtual Packet

Current host

Data server

Host database

Internet address manipulation

Miscellaneous

Network database

Network protocol database

Network services database

Protocols

Remote hosts

Resolver

SNMP messages

Sockets

Socket messages

SOCKS server

Virtual Packet

What's in a function description?

Each function page consists of a number of subsections:

• Synopsis
• Description
• Returns
• Errors
• Examples
• Classification
• Caveats
• See also

Synopsis:

Gives the header files that should be included within a source file that references the function or macro. It also shows an appropriate declaration for the function or for a function that could be substituted for a macro. This declaration isn't included in your program; only the header file(s) should be included.

When a pointer argument is passed to a function, and that function doesn't modify the item indicated by that pointer, then the argument is shown with const before the argument. For example, the following indicates that the array pointed at by string isn't changed:

    const char * string

Description:

A description of the function or macro.

Returns:

The return value (if any) for the function or macro.

Errors:

Describes the possible values that the function might assign to the global variable errno.

Examples:

Consists of one or more examples that demonstrate the use of the function. The examples are often just fragments of code (not complete programs) for illustrative purposes. This subsection is optional.

Classification:

Provides an indication of where the function or macro is commonly found. The following notation is used:

POSIX 1003.1g (Draft: Protocol Independent Interfaces)

These functions are specified in the document Information Technology - Portable Operating System Interface (POSIX) Part 1g: Protocol Independent Interfaces (PII). This draft document defines a programmatic interface for network process-to-process communication, such that the application may be independent of the underlying protocols. Note that it's a draft document and is subject to change.

QNX 4

These functions or macros are neither ANSI nor POSIX. They perform a function related to QNX 4. They may be found in other implementations of C for personal computers with QNX 4. Use these functions with caution if portability is a consideration.

SNMP

Simple Network Management Protocol is a network-management protocol whose base document is RFC 1067. It's used to query and modify network device states.

SOCKS

These functions are part of the SOCKS package consisting of a proxy server, client programs (rftp and rtelnet), and a library (libsocks.a) for adapting other applications into new client programs. For more information, see the appendix SOCKS - A Basic Firewall.

UNIX

These functions exist on some UNIX systems, but are outside of the POSIX or ANSI standards.

We've created the following Unix categories to differentiate:

Legacy Unix

Functions included for backwards compatibility only. New applications shouldn't implement these functions.

Standard Unix

Functions that match XOPEN specifications.

Unix

Unix functions that don't fall into the above two categories. ;-)

Function safety:

Indicates whether or not it's safe to use the TCP/IP function in:

• an interrupt handler
• a signal handler
• a multithreaded program

Interrupt handler

An interrupt-safe function behaves as documented even if used in an interrupt handler. Functions flagged as interrupt-unsafe shouldn't be used in interrupt handlers.

Signal handler

A signal-safe function behaves as documented even if called from a signal handler even if the signal interrupts a signal-unsafe function.

Some of the signal-safe functions modify errno on failure. If you use any of these in a signal handler, asynchronous signals may have the side effect of modifying errno in an unpredictable way. If any of the code that can be interrupted checks the value of errno (this also applies to library calls, so you should assume that most library calls may internally check errno), make sure that your signal handler saves errno on entry and restores it on exit.

All of the above also applies to signal-unsafe functions, with one exception: if a signal handler calls a signal-unsafe function, make sure that signal doesn't interrupt a signal-unsafe function.

Thread

A thread-safe function behaves as documented even if called in a multi-threaded environment.

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The "safety" designations documented in this manual are valid for the the TCP/IP 5.0 release and could change in future versions.

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Caveats:

Gives warnings about the function.

See also:

Provides a list of related functions or macros, or places to look for more information. This subsection is optional.