getservbyport (3p) - Linux Manuals

PROLOG

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME

endservent, getservbyname, getservbyport, getservent, setservent - network services database functions

SYNOPSIS

#include <netdb.h>

void endservent(void);
struct servent *getservbyname(const char *name, const char *proto);
struct servent *getservbyport(int port, const char *proto);
struct servent *getservent(void);
void setservent(int stayopen);

DESCRIPTION

These functions shall retrieve information about network services. This information is considered to be stored in a database that can be accessed sequentially or randomly. The implementation of this database is unspecified.

The setservent() function shall open a connection to the database, and set the next entry to the first entry. If the stayopen argument is non-zero, the net database shall not be closed after each call to the getservent() function (either directly, or indirectly through one of the other getserv*() functions), and the implementation may maintain an open file descriptor for the database.

The getservent() function shall read the next entry of the database, opening and closing a connection to the database as necessary.

The getservbyname() function shall search the database from the beginning and find the first entry for which the service name specified by name matches the s_name member and the protocol name specified by proto matches the s_proto member, opening and closing a connection to the database as necessary. If proto is a null pointer, any value of the s_proto member shall be matched.

The getservbyport() function shall search the database from the beginning and find the first entry for which the port specified by port matches the s_port member and the protocol name specified by proto matches the s_proto member, opening and closing a connection to the database as necessary. If proto is a null pointer, any value of the s_proto member shall be matched. The port argument shall be in network byte order.

The getservbyname(), getservbyport(), and getservent() functions shall each return a pointer to a servent structure, the members of which shall contain the fields of an entry in the network services database.

The endservent() function shall close the database, releasing any open file descriptor.

These functions need not be reentrant. A function that is not required to be reentrant is not required to be thread-safe.

RETURN VALUE

Upon successful completion, getservbyname(), getservbyport(), and getservent() return a pointer to a servent structure if the requested entry was found, and a null pointer if the end of the database was reached or the requested entry was not found. Otherwise, a null pointer is returned.

ERRORS

No errors are defined.

The following sections are informative.

EXAMPLES

None.

APPLICATION USAGE

The port argument of getservbyport() need not be compatible with the port values of all address families.

The getservbyname(), getservbyport(), and getservent() functions may return pointers to static data, which may be overwritten by subsequent calls to any of these functions.

RATIONALE

None.

FUTURE DIRECTIONS

None.

COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .