Sockets and Networking

The Interix Software Development Kit (SDK) implements BSD-style socket interfaces, including bind() , accept() , and connect() . The Interix SDK implementation uses the Windows network stack, through the use of Winsock to access the network. This means that TCP/IP sockets and all of the installed Winsock protocols are supported.

For more information about Winsock, see the Winsock documentation at http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winsock/wsapiref_7v1u.asp .

Exceptions to socket support in Interix are discussed in the following sections:

• Host Name to Address Translation

• Network Groups

• Network Socket Calls

• Transport Level Interface (XTI) Calls

Host Name to Address Translation

Interix does not support the generic transport name-to-address translation routines. Interix does support the gethostby routines, except for the re-entrant versions (thatis, routines with the _r suffix). Table 10.18 shows other host or domain name get or set routines not supported by Interix.

Table 10.18: Host Name Translation Routines Not Supported by Interix

Function Name	Description	Suggested Interix Replacement
getdomainname	Gets the NIS domain name.	No equivalent in Interix. The principal Windows domain for the system can be obtained through getpdomain() .
gethostid	Gets the unique identifier of the current host.	No equivalent in Interix, but should be a very rare occurrence in any application except a network administration application.
gethostbyaddr_r, gethostbyname_r, gethostent_r	Re-entrant safe versions.	Replace with equivalents lacking the _r suffix. Interix is not multithreaded, and therefore does not need to support the re-entrant versions.
setdomainname	Sets the NIS domain name.	No equivalent in Interix.
sethostid	Sets the unique identifier of the current host.	No equivalent in Interix, but should never need to be set. It is restricted to the root user account.
sethostname	Sets the name of the host computer. (This call is restricted to the superuser and is normally used only when the system is booted .)	No equivalent in Interix.

Network Groups

Interix does not currently support the network group APIs. However, it does support network group designations in hosts .equiv and .rhosts files.

Network Socket Calls

These functions constitute the BSD sockets library. Interix provides all network functions in the main C library, libc.a; for compatibility, Interix includes an empty lisocket.a library.

Interix supports all the socket calls except those summarized in Table 10.19 and Table 10.20.

Table 10.19: Socket Calls Not Supported by Interix

Function Name	Description	Suggested Interix Replacement
cmsg macros	Access ancillary data.	No equivalent in Interix.
freeaddrinfo	Removes address entry from linked list.	Currently no API support for IPv6.
freehostent	Removes IP node entry from linked list.	Currently no API support for IPv6.
gai_strerror	Helps applications print error messages based on the EAI_*codes returned by getaddrinfo .	Currently no API support for IPv6.
getaddrinfo	Translates between node name and address.	Currently no API support for IPv6.
getipnodebyaddr	Gets IP node entry.	Currently no API support for IPv6.
getipnodebyname	Gets IP node entry.	Currently no API support for IPv6.
getnameinfo	Translates between node name and address.	Currently no API support for IPv6.
inet_ntop	Processes network address structures.	Currently no API support for IPv6.
inet_pton	Creates a network address structure.	Currently no API support for IPv6.
rcmd_af	Returns a stream to a remote command and includes support for Ipv6.	Currently no API support for IPv6.
recvmsg	Receives a message from a socket.	No equivalent in Interix.
rexec_af	Returns a stream to a remote command and includes support for Ipv6.	Currently no API support for IPv6.
rresvport_af		Currently no API support for IPv6.
sendmsg	Sends a message to a socket.	No equivalent in Interix.

The two sockets functions recvmsg and sendmsg appear in many network applications but are not supported by Interix. These functions are the only way to passan open file descriptor from one running process to another running process.

For examples of UNIX code using sockets that port directly to Interix, see Sockets and Networking in Chapter 9, Win32 Code Conversion.

Each re-entrant interface performs the same operation as its non-re-entrant counterpart . The only difference is the _r suffix. The re-entrant interfaces, however, use buffers supplied by the caller to store returned results, and they are safe for usein both single-threaded and multithreaded applications. If the application is not multithreaded, then the _r routines can be safely replaced by removing the _r suffix and the additional parameters.

Table 10.20: Interix Replacements for Re-entrant Routines

Function Name	Description	Suggested Interix Replacement
getnetbyaddr_r	Searches for a network entry with the network address.	getnetbyaddr
getnetbyname_r	Searches for a network entry with specified name.	getnetbyname
getnetent_r	Enumerates network entries from the database.	getnetent
getprotobyname_r	Sequentially searches from the beginning of the file until a matching protocol name is found, or EOF is encountered .	getprotobyname
getprotobynumber_r	Sequentially searches from the beginning of the file until a matching protocol number is found, or EOF is encountered.	getprotobynumber
getprotoent_r	Gets a matching protocol name.	getprotoent
getservbyname_r	Returns a pointer to an object containing the information from a network services database.	getservbyname
getservbyport_r	Returns a pointer to an object containing the information from a network services database.	getservbyport
getservent_r	Returns a pointer to an object containing the information from a network services database.	getservent

Transport Level Interface (XTI) Calls

The XTI APIs, defined by The Open Group s X/Open Transport Interface specification, define protocol-independent networking functions similar to those providedby the old SVR4 TLI (Transport Level Interface) APIs. XTI, and TLI before it, were primarily used as interfaces to the ISO OSI protocol family or to the STREAMS networking stack. In general, use of XTI should be replaced by use of the more standard BSD Sockets interface.

Interix support for XTI is limited solely to the functions and features required to access the UDP Internet protocol. Interix does not support some extended calls(see Table 10.21), which are mainly used with expedited data and the management or configuration of variables and parameters.

Table 10.21: Transport-level Interface Calls Not Supported by Interix

Function Name	Description	Suggested Interix Replacement
nlsgetcall	Gets client data passed via the listener.	No equivalent in Interix.
nlsprovider	Gets the name of the transport provider.	No equivalent in Interix.
nlsrequest	Formats and sends a listener service request message.	No equivalent in Interix.
t_rcvv	Receives data or expedited data sent over a connection and puts data into one or more noncontiguous buffers greater than or equal to.	No equivalent in Interix.
t_rcvvudata	Receives a data unit in one or more noncontiguous buffers.	No equivalent in Interix.
t_sndv	Sends data or expedited data from one or more noncontiguous buffers on a connection.	No equivalent in Interix.
t_sndvudata	Sends a data unit from one or more noncontiguous buffers.	No equivalent in Interix.
t_sysconf	Gets configurable XTI variables.	No equivalent in Interix.