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getservbyport(3)
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getservbyport, getservbyport_r - Get a service entry by
port number
#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 );
Standard C Library (libc)
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.
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 getservbyport_r()
only, this points to the servent structure. The
netdb.h header file defines the servent structure. [Tru64
UNIX] For getservbyport_r() only, this is data for the
services database. The netdb.h header file defines the
servent_data structure.
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.
The getservbyport() function returns a pointer to threadspecific
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.
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.
[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.
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. The database service selection
configuration file.
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
getservbyport(3)
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