/*
* %CopyrightBegin%
*
* Copyright Ericsson AB 2000-2013. All Rights Reserved.
*
* The contents of this file are subject to the Erlang Public License,
* Version 1.1, (the "License"); you may not use this file except in
* compliance with the License. You should have received a copy of the
* Erlang Public License along with this software. If not, it can be
* retrieved online at http://www.erlang.org/.
*
* Software distributed under the License is distributed on an "AS IS"
* basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
* the License for the specific language governing rights and limitations
* under the License.
*
* %CopyrightEnd%
*/
package com.ericsson.otp.erlang;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.net.InetAddress;
import java.net.Socket;
/**
* Provides methods for registering, unregistering and looking up nodes with the
* Erlang portmapper daemon (Epmd). For each registered node, Epmd maintains
* information about the port on which incoming connections are accepted, as
* well as which versions of the Erlang communication protocolt the node
* supports.
*
* <p>
* Nodes wishing to contact other nodes must first request information from Epmd
* before a connection can be set up, however this is done automatically by
* {@link OtpSelf#connect(OtpPeer) OtpSelf.connect()} when necessary.
*
* <p>
* The methods {@link #publishPort(OtpLocalNode) publishPort()} and
* {@link #unPublishPort(OtpLocalNode) unPublishPort()} will fail if an Epmd
* process is not running on the localhost. Additionally
* {@link #lookupPort(AbstractNode) lookupPort()} will fail if there is no Epmd
* process running on the host where the specified node is running. See the
* Erlang documentation for information about starting Epmd.
*
* <p>
* This class contains only static methods, there are no constructors.
*/
public class OtpEpmd {
private static class EpmdPort {
private static int epmdPort = 0;
public static int get() {
if (epmdPort == 0) {
String env;
try {
env = System.getenv("ERL_EPMD_PORT");
}
catch (java.lang.SecurityException e) {
env = null;
}
epmdPort = (env != null) ? Integer.parseInt(env) : 4369;
}
return epmdPort;
}
public static void set(int port) {
epmdPort = port;
}
}
// common values
private static final byte stopReq = (byte) 115;
private static final byte port4req = (byte) 122;
private static final byte port4resp = (byte) 119;
private static final byte publish4req = (byte) 120;
private static final byte publish4resp = (byte) 121;
private static final byte names4req = (byte) 110;
private static int traceLevel = 0;
private static final int traceThreshold = 4;
static {
// debug this connection?
final String trace = System.getProperties().getProperty(
"OtpConnection.trace");
try {
if (trace != null) {
traceLevel = Integer.valueOf(trace).intValue();
}
} catch (final NumberFormatException e) {
traceLevel = 0;
}
}
// only static methods: no public constructors
// hmm, idea: singleton constructor could spawn epmd process
private OtpEpmd() {
}
/**
* Set the port number to be used to contact the epmd process.
* Only needed when the default port is not desired and system environment
* variable ERL_EPMD_PORT can not be read (applet).
*/
public static void useEpmdPort(int port) {
EpmdPort.set(port);
}
/**
* Determine what port a node listens for incoming connections on.
*
* @return the listen port for the specified node, or 0 if the node was not
* registered with Epmd.
*
* @exception java.io.IOException
* if there was no response from the name server.
*/
public static int lookupPort(final AbstractNode node) throws IOException {
return r4_lookupPort(node);
}
/**
* Register with Epmd, so that other nodes are able to find and connect to
* it.
*
* @param node
* the server node that should be registered with Epmd.
*
* @return true if the operation was successful. False if the node was
* already registered.
*
* @exception java.io.IOException
* if there was no response from the name server.
*/
public static boolean publishPort(final OtpLocalNode node)
throws IOException {
Socket s = null;
s = r4_publish(node);
node.setEpmd(s);
return s != null;
}
// Ask epmd to close his end of the connection.
// Caller should close his epmd socket as well.
// This method is pretty forgiving...
/**
* Unregister from Epmd. Other nodes wishing to connect will no longer be
* able to.
*
* <p>
* This method does not report any failures.
*/
public static void unPublishPort(final OtpLocalNode node) {
Socket s = null;
try {
s = new Socket((String) null, EpmdPort.get());
@SuppressWarnings("resource")
final OtpOutputStream obuf = new OtpOutputStream();
obuf.write2BE(node.alive().length() + 1);
obuf.write1(stopReq);
obuf.writeN(node.alive().getBytes());
obuf.writeTo(s.getOutputStream());
// don't even wait for a response (is there one?)
if (traceLevel >= traceThreshold) {
System.out.println("-> UNPUBLISH " + node + " port="
+ node.port());
System.out.println("<- OK (assumed)");
}
} catch (final Exception e) {/* ignore all failures */
} finally {
try {
if (s != null) {
s.close();
}
} catch (final IOException e) { /* ignore close failure */
}
s = null;
}
}
private static int r4_lookupPort(final AbstractNode node)
throws IOException {
int port = 0;
Socket s = null;
try {
@SuppressWarnings("resource")
final OtpOutputStream obuf = new OtpOutputStream();
s = new Socket(node.host(), EpmdPort.get());
// build and send epmd request
// length[2], tag[1], alivename[n] (length = n+1)
obuf.write2BE(node.alive().length() + 1);
obuf.write1(port4req);
obuf.writeN(node.alive().getBytes());
// send request
obuf.writeTo(s.getOutputStream());
if (traceLevel >= traceThreshold) {
System.out.println("-> LOOKUP (r4) " + node);
}
// receive and decode reply
// resptag[1], result[1], port[2], ntype[1], proto[1],
// disthigh[2], distlow[2], nlen[2], alivename[n],
// elen[2], edata[m]
final byte[] tmpbuf = new byte[100];
final int n = s.getInputStream().read(tmpbuf);
if (n < 0) {
s.close();
throw new IOException("Nameserver not responding on "
+ node.host() + " when looking up " + node.alive());
}
@SuppressWarnings("resource")
final OtpInputStream ibuf = new OtpInputStream(tmpbuf, 0);
final int response = ibuf.read1();
if (response == port4resp) {
final int result = ibuf.read1();
if (result == 0) {
port = ibuf.read2BE();
node.ntype = ibuf.read1();
node.proto = ibuf.read1();
node.distHigh = ibuf.read2BE();
node.distLow = ibuf.read2BE();
// ignore rest of fields
}
}
} catch (final IOException e) {
if (traceLevel >= traceThreshold) {
System.out.println("<- (no response)");
}
throw new IOException("Nameserver not responding on " + node.host()
+ " when looking up " + node.alive());
} catch (final OtpErlangDecodeException e) {
if (traceLevel >= traceThreshold) {
System.out.println("<- (invalid response)");
}
throw new IOException("Nameserver not responding on " + node.host()
+ " when looking up " + node.alive());
} finally {
try {
if (s != null) {
s.close();
}
} catch (final IOException e) { /* ignore close errors */
}
s = null;
}
if (traceLevel >= traceThreshold) {
if (port == 0) {
System.out.println("<- NOT FOUND");
} else {
System.out.println("<- PORT " + port);
}
}
return port;
}
/*
* this function will get an exception if it tries to talk to a
* very old epmd, or if something else happens that it cannot
* forsee. In both cases we return an exception. We no longer
* support r3, so the exception is fatal. If we manage to
* successfully communicate with an r4 epmd, we return either the
* socket, or null, depending on the result.
*/
private static Socket r4_publish(final OtpLocalNode node)
throws IOException {
Socket s = null;
try {
@SuppressWarnings("resource")
final OtpOutputStream obuf = new OtpOutputStream();
s = new Socket((String) null, EpmdPort.get());
obuf.write2BE(node.alive().length() + 13);
obuf.write1(publish4req);
obuf.write2BE(node.port());
obuf.write1(node.type());
obuf.write1(node.proto());
obuf.write2BE(node.distHigh());
obuf.write2BE(node.distLow());
obuf.write2BE(node.alive().length());
obuf.writeN(node.alive().getBytes());
obuf.write2BE(0); // No extra
// send request
obuf.writeTo(s.getOutputStream());
if (traceLevel >= traceThreshold) {
System.out.println("-> PUBLISH (r4) " + node + " port="
+ node.port());
}
// get reply
final byte[] tmpbuf = new byte[100];
final int n = s.getInputStream().read(tmpbuf);
if (n < 0) {
s.close();
throw new IOException("Nameserver not responding on "
+ node.host() + " when publishing " + node.alive());
}
@SuppressWarnings("resource")
final OtpInputStream ibuf = new OtpInputStream(tmpbuf, 0);
final int response = ibuf.read1();
if (response == publish4resp) {
final int result = ibuf.read1();
if (result == 0) {
node.creation = ibuf.read2BE();
if (traceLevel >= traceThreshold) {
System.out.println("<- OK");
}
return s; // success
}
}
} catch (final IOException e) {
// epmd closed the connection = fail
if (s != null) {
s.close();
}
if (traceLevel >= traceThreshold) {
System.out.println("<- (no response)");
}
throw new IOException("Nameserver not responding on " + node.host()
+ " when publishing " + node.alive());
} catch (final OtpErlangDecodeException e) {
s.close();
if (traceLevel >= traceThreshold) {
System.out.println("<- (invalid response)");
}
throw new IOException("Nameserver not responding on " + node.host()
+ " when publishing " + node.alive());
}
s.close();
return null;
}
public static String[] lookupNames() throws IOException {
return lookupNames(InetAddress.getByName(null));
}
public static String[] lookupNames(final InetAddress address)
throws IOException {
Socket s = null;
try {
@SuppressWarnings("resource")
final OtpOutputStream obuf = new OtpOutputStream();
try {
s = new Socket(address, EpmdPort.get());
obuf.write2BE(1);
obuf.write1(names4req);
// send request
obuf.writeTo(s.getOutputStream());
if (traceLevel >= traceThreshold) {
System.out.println("-> NAMES (r4) ");
}
// get reply
final byte[] buffer = new byte[256];
final ByteArrayOutputStream out = new ByteArrayOutputStream(256);
while (true) {
final int bytesRead = s.getInputStream().read(buffer);
if (bytesRead == -1) {
break;
}
out.write(buffer, 0, bytesRead);
}
final byte[] tmpbuf = out.toByteArray();
@SuppressWarnings("resource")
final OtpInputStream ibuf = new OtpInputStream(tmpbuf, 0);
ibuf.read4BE(); // read port int
// final int port = ibuf.read4BE();
// check if port = epmdPort
final int n = tmpbuf.length;
final byte[] buf = new byte[n - 4];
System.arraycopy(tmpbuf, 4, buf, 0, n - 4);
final String all = OtpErlangString.newString(buf);
return all.split("\n");
} finally {
if (s != null) {
s.close();
}
}
} catch (final IOException e) {
if (traceLevel >= traceThreshold) {
System.out.println("<- (no response)");
}
throw new IOException(
"Nameserver not responding when requesting names");
} catch (final OtpErlangDecodeException e) {
if (traceLevel >= traceThreshold) {
System.out.println("<- (invalid response)");
}
throw new IOException(
"Nameserver not responding when requesting names");
}
}
}
