GetServiceByName class provides lookup of port numbers in
* the /etc/services file.
* NIS service lookup isn't provided (at least yet).
*
* @author Dan Anderson
* @version $Id$
*/
public class GetServiceByName {
final static private String SERVICES_FILENAME
= "/etc/services"; // aka /etc/inet/services
// c:\winnt\system32\drivers\etc\services on Win NT/2000
/**
* The parseServicesLine() method
* is called by getPortNumberForTcpIpService() to parse
* a non-comment line in the /etc/services file
* and save the values.
*
* @param line
* A line to compare from the /etc/services file.
*
* @param tcpipService
* The name of a TCP/IP "well-known" service found in the
* /etc/services file
*
* @param tcpipClass
* Either "tcp" or "udp", depending on the TCP/IP service desired.
*
* @return
* A port number for a TCP or UDP service (depending on tcpipClass).
* Return -1 on error.
*/
static private int parseServicesLine(String line,
String tcpipService,
String tcpipClass) {
// Parse line
StringTokenizer st = new
StringTokenizer(line, " \t/#");
// First get the name on the line (parameter 1):
if (! st.hasMoreTokens()) {
return -1; // error
}
String name = st.nextToken().trim();
// Next get the service name on the line (parameter 2):
if (! st.hasMoreTokens()) {
return -1; // error
}
String portValue = st.nextToken().trim();
// Finally get the class on the line (parameter 3):
if (! st.hasMoreTokens()) {
return -1; // error
}
String classValue = st.nextToken().trim();
//System.out.println("DEBUG: name: "
// + name + ", portValue: " + portValue
// + ", serviceValue: " + serviceValue);
// Class doesn't match--reject:
if (! classValue.equals(tcpipClass)) {
return -1; // error
}
// Return port number, if name on this line matches:
if (name.equals(tcpipService)) {
try { // Convert the port number string to integer
return (Integer.parseInt(portValue));
} catch (NumberFormatException nfe) {
// Ignore corrupt /etc/services lines:
return -1; // error
}
} else {
return -1; // no match
}
} // parseServicesLine()
/**
* The getServiceByName() method
* Search the /etc/services file for a service name and class.
* Return the port number.
* * For example, given this line in /etc/services, *
* farkle 4545/udp ** In this example, a search for service "farkle" and class "udp" * will return 4545. * * @param tcpipService * The name of a TCP/IP "well-known" service found in the * /etc/services file * * @param tcpipClass * Either "tcp" or "udp", depending on the TCP/IP service desired. * * @return * A port number for a TCP or UDP service * (depending on tcpipClass). * Return -1 on error. */ static public int getServiceByName(String tcpipService, String tcpipClass) { int port = -1; // Look for our service, line-by-line: try { String line; BufferedReader br = new BufferedReader( new InputStreamReader( new FileInputStream( SERVICES_FILENAME))); // Read /etc/services file. // Skip comments and empty lines. while (((line = br.readLine()) != null) && (port == -1)) { if ((line.length() != 0) && (line.charAt(0) != '#')) { port = parseServicesLine(line, tcpipService, tcpipClass); } } // while br.close(); return (port); // port number or -1 (on error) } catch (IOException ioe) { // File doesn't exist or is otherwise not available. // Keep defaults return -1; // error } } // getServiceByName /** * The
main() method
* is for use as an internal test driver only.
*
* To execute: set $CLASSPATH and run:
* java GetServiceByName
* [tcpipService tcpipClass]
*
* where service is a TCP/IP service and class is a
* TCP/IP class (either "tcp" or "udp").
*
* For example: * java GetServiceByName ftp tcp *
* Exit code is 0 on success, non-zero on failure.
*
* @param tcpipService
* The service name for which the port number is desired.
* @param tcpipClass
* The TCP/IP class (either "tcp" or "udp")
*/
public static void main(String args[]) {
int pok, png;
int errorCount = 0;
try {
// Check for arguments on command line
if ((args.length != 0) && (args.length != 2)) {
System.err.println(
"Test driver for this class\n"
+ "Usage: "
+ "java GetServiceByName "
+ "[