getservbyport_r - Linux
Overview
getservbyport_r
is a Linux command used to retrieve service information for a given port number. It’s primarily used in network programming to associate port numbers with their corresponding service names.
Syntax
#include <netdb.h>
int getservbyport_r(int port, const struct protoent *protocol,
struct servent *result_buf, char *buf, size_t buflen,
struct servent **result);
Options/Flags
port
: The port number to retrieve information for.protocol
: The transport layer protocol (e.g., TCP, UDP) to use for the lookup.result_buf
: A pointer to astruct servent
to store the retrieved service information.buf
: A buffer to store the service name in.buflen
: The size of thebuf
buffer in bytes.result
: A pointer to astruct servent **
that will be set to theresult_buf
if the lookup succeeds.
Examples
Get service information for TCP port 80:
#include <netdb.h>
struct servent *serv_info;
int status;
status = getservbyport_r(htons(80), getprotobyname("tcp"),
serv_info, buf, buflen, &serv_info);
if (status == 0) {
printf("Service: %s\n", serv_info->s_name);
} else {
perror("getservbyport_r");
}
Common Issues
- Ensure that the
protocol
argument is a valid transport layer protocol name (e.g., TCP, UDP). - Make sure the
buflen
is large enough to hold the service name.
Integration
getservbyport_r
can be used in conjunction with other network programming functions such as socket
, connect
, and send
. It’s particularly useful when working with various network services and handling inbound connections on specific ports.
Related Commands
getservbyname_r
: Retrieves service information by service name.getprotobynumber_r
: Retrieves protocol information by protocol number.