getservbyport(3) Library Functions Manual getservbyport(3)
NAME
getservbyport, getservbyport_r - Get a service entry by port number
LIBRARY
Standard C Library (libc.so, libc.a)
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 oper-
ating 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);
STANDARDS
Interfaces documented on this reference page conform to industry standards as follows:
getservbyport(): XNS4.0
Refer to the standards(5) reference page for more information about industry standards and associated tags.
PARAMETERS
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. Specifies the protocol name to use when contacting the service. [Tru64 UNIX] For get-
servbyport_r() only, this points to the servent structure. The netdb.h header file defines the servent structure. [Tru64 UNIX] For get-
servbyport_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 spec-
ified (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:
The serv or serv_data parameter is invalid. The search failed.
In addition, if the function fails to open the file, it sets errno to indicate the cause of the failure.
FILES
The DARPA 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. The database service selection configuration file.
RELATED INFORMATION
Functions: getservbyname(3), getservent(3), setservent(3), endservent(3)
Files: services(4), svc.conf(4).
Networks: nis_intro(7).
Standards: standards(5). delim off
getservbyport(3)