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getservbyport(3)
NAME
  getservbyport, getservbyport_r - Get a service entry by port number

SYNOPSIS
  #include <netdb.h>

  struct servent *getservbyport(
	  int port,
	  const char *proto );

  [Tru64 UNIX]	The following obsolete function is supported in order to
  maintain backward compatibility with previous versions of the operating
  system.  You should not use it in new designs.

  int getservbyport_r(
	  int port,
	  const char *proto,
	  struct servent *serv,
	  struct servent_data *serv_data );

LIBRARY
  Standard C Library (libc)

STANDARDS
  Interfaces documented on this reference page conform to industry standards
  as follows:

  getservbyport():  XNS4.0, XNS5.0

  Refer to the standards(5) reference page for more information about
  industry standards and associated tags.

PARAMETERS
  port
      Specifies the port number where the service is located. This argument
      must be converted from host-byte order to a 2-byte Internet network
      integer through a call to the htons() function.

  proto
      Specifies the protocol name to use when contacting the service.

  serv
      [Tru64 UNIX]  For getservbyport_r() only, this points to the servent
      structure.  The netdb.h header file defines the servent structure.

  serv_data
      [Tru64 UNIX]  For getservbyport_r() only, this is data for the services
      database.	 The netdb.h header file defines the servent_data structure.

DESCRIPTION
  The getservbyport() function returns a pointer to a structure of type
  servent. Its members specify data in fields from a record line in either
  the local /etc/services file or the NIS distributed network services
  database file. To determine which file or files to search, and in which
  order, the system uses the switches in the /etc/svc.conf file. The netdb.h
  header file defines the servent structure.

  The getservbyport() function searches the network services database file
  sequentially until a match with the port parameter and with the proto
  parameter occurs. When used, the proto parameter must specify the network
  services protocol name. When the protocol name is not specified (the proto
  parameter is NULL), the proto parameter need not be matched during the
  network services database file record search. When EOF (End-of-File) is
  reached without a match, a null pointer is returned by this function.

  Use the endservent() function to close the network services database file.

NOTES
  The getservbyport() function returns a pointer to thread-specific data.
  Subsequent calls to this or a related function from the same thread
  overwrite this data.

  [Tru64 UNIX]	The getservbyport_r() function is an obsolete reentrant
  version of the getservbyport() function.  It is supported in order to
  maintain backward compatibility with previous versions of the operating
  system and should not be used in new designs.	 Note that you must zero-fill
  the servent_data structure before its first access by either the
  setservent_r() or getservbyport_r() function.

RETURN VALUES
  Upon successful completion, the getservbyport() function returns a pointer
  to a servent structure.  If it fails or reaches the end of the network
  services database file, it returns a null pointer.

  [Tru64 UNIX]	Upon successful completion, the getservbyport_r() function
  stores the servent structure in the location pointed to by serv, and
  returns a value of 0 (zero).	Upon failure, it returns a value of -1.

ERRORS
  [Tru64 UNIX]	If any of the following conditions occurs, the
  getservbyport_r() function sets errno to the corresponding value:

  [EINVAL]
      The serv or serv_data parameter is invalid.

  [ESRCH]
      The search failed.

  In addition, if the function fails to open the file, it sets errno to
  indicate the cause of the failure.

FILES
  /etc/services
      The Internet network service name database file. Each record in the
      file occupies a single line and has four fields: the official service
      name, the port number, the protocol name, and aliases.

  /etc/svc.conf
      The database service selection configuration file.

SEE ALSO
  Functions: getservbyname(3), getservent(3), setservent(3), endservent(3)

  Files: services(4), svc.conf(4).

  Networks: nis_intro(7).

  Standards: standards(5).

  Network Programmer's Guide

Index for Section 3

Alphabetical listing for G

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