getservbyport()

The getservbyport() call returns a pointer to the ETC\SERVICES file entry specified by a port number.

Syntax

#include <netdb.h>
struct servent *getservbyport(port, proto)
int port;
char *proto;

Parameters

port

Specified port.

Pointer to the specified protocol.

Description

This call sequentially searches the ETC\SERVICES file for the specified port number, which must match the protocol if a protocol is stated.

The getservbyport() call retrieves an entry from the ETC\SERVICES file using the port parameter as a search key.

An application program can use this call to access a service, service aliases, the protocol for the service, and a protocol port number for the service.

The getservbyname() call searches the ETC\SERVICES file sequentially from the start of the file until it finds one of the following:

• Matching protocol and port number 
  Matching protocol when the port parameter is set to 0
  
  End of the file
  Upon locating a matching protocol and port number-or upon locating a matching protocol only (if the port parameter equals 0-the getservbyport() call returns a pointer to the servent structure. This structure contains fields for a line of information from the ETC\SERVICES file. The <NETDB.H> file defines the servent structure and structure fields.

  Use the endservent() call to close the ETC\SERVICES file.

  Return Values

  The getservbyport() call returns a pointer to a servent structure for the port number specified on the call. The return value points to static data that subsequent API calls can modify. A pointer to a servent structure indicates success. A NULL pointer indicates an error or EOF.

  The servent structure is defined in the <NETDB.H> header file and contains the following elements:

  Element

  Description
  s _ name
  Officialnameoftheservice
  s _ aliases
  Array ,terminatedwithaNULLpointer ,ofalternativenamesfortheservice
  s _ port
  Portnumberoftheservice
  s _ proto
  Requiredprotocoltocontacttheservice

  Related Calls

  endprotoent() endservent()
  getprotobyname()
  getprotoent()
  getservbyname()
  getservent()
  setprotoent()
  setservent()

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