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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); [Digital] 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); STANDARDS Interfaces documented on this reference page conform to industry stan- dards as follows: getservbyport(): XPG4-UNIX Refer to the standards(5) reference page for more information about in- dustry 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 in- teger through a call to the htons function. Specifies the protocol name to use when contacting the service. [Digital] For getservby- port_r() only, this points to the servent structure. The netdb.h header file defines the servent structure. [Digital] For getservby- port_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 ei- ther the local /etc/services file or the NIS distributed network ser- vices 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. [Digital] The getservbyport_r() function is an obsolete reentrant ver- sion 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. [Digital] 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 [Digital] If any of the following conditions occurs, the getservby- port_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 ser- vice name, the port number, the protocol name, and aliases. The data- base service selection configuration file. RELATED INFORMATION Functions: getservbyname(3), getservent(3), setservent(3), endser- vent(3) Files: services(4), svc.conf(4). Networks: nis_intro(7). Standards: standards(5). delim off getservbyport(3)