+++ /dev/null
-package edu.uci.iotproject.trafficreassembly.layer3;
-
-import edu.uci.iotproject.analysis.TcpConversationUtils;
-import edu.uci.iotproject.util.PcapPacketUtils;
-import org.pcap4j.core.PcapPacket;
-import org.pcap4j.packet.IpV4Packet;
-import org.pcap4j.packet.Packet;
-import org.pcap4j.packet.TcpPacket;
-
-import java.util.*;
-
-/**
- * Models a (TCP) conversation/connection/session/flow (packet's belonging to the same session between a client and a
- * server).
- * Holds a list of {@link PcapPacket}s identified as pertaining to the flow. Note that this list is <em>not</em>
- * considered when determining equality of two {@code Conversation} instances in order to allow for a
- * {@code Conversation} to function as a key in data structures such as {@link java.util.Map} and {@link java.util.Set}.
- * See {@link #equals(Object)} for the definition of equality.
- *
- * @author Janus Varmarken {@literal <jvarmark@uci.edu>}
- * @author Rahmadi Trimananda {@literal <rtrimana@uci.edu>}
- */
-public class Conversation {
-
- /* Begin instance properties */
- /**
- * The IP of the host that is considered the client (i.e. the host that initiates the conversation)
- * in this conversation.
- */
- private final String mClientIp;
-
- /**
- * The port number used by the host that is considered the client in this conversation.
- */
- private final int mClientPort;
-
- /**
- * The IP of the host that is considered the server (i.e. is the responder) in this conversation.
- */
- private final String mServerIp;
-
- /**
- * The port number used by the server in this conversation.
- */
- private final int mServerPort;
-
- /**
- * The list of packets (with payload) pertaining to this conversation.
- */
- private final List<PcapPacket> mPackets;
-
- /**
- * If {@link #isTls()} is {@code true}, this list contains the subset of {@link #mPackets} which are TLS Application
- * Data packets.
- */
- private final List<PcapPacket> mTlsApplicationDataPackets;
-
- /**
- * Contains the sequence numbers used thus far by the host that is considered the <em>client</em> in this
- * {@code Conversation}.
- * Used for filtering out retransmissions.
- */
- private final Set<Integer> mSeqNumbersClient;
-
- /**
- * Contains the sequence numbers used thus far by the host that is considered the <em>server</em> in this
- * {@code Conversation}.
- * Used for filtering out retransmissions.
- */
- private final Set<Integer> mSeqNumbersSrv;
-
- /**
- * List of SYN packets pertaining to this conversation.
- */
- private final List<PcapPacket> mSynPackets;
-
- /**
- * List of pairs FINs and their corresponding ACKs associated with this conversation.
- */
- private final List<FinAckPair> mFinPackets;
-
- /**
- * List of RST packets associated with this conversation.
- */
- private final List<PcapPacket> mRstPackets;
-
- /**
- * Boolean to mark the packet as Application Data based on the previous packet that reaches MTU
- */
- private boolean mApplicationData;
- /* End instance properties */
-
- /**
- * Factory method for creating a {@code Conversation} from a {@link PcapPacket}.
- * @param pcapPacket The {@code PcapPacket} that wraps a TCP segment for which a {@code Conversation} is to be initiated.
- * @param clientIsSrc If {@code true}, the source address and source port found in the IP datagram and TCP segment
- * wrapped in the {@code PcapPacket} are regarded as pertaining to the client, and the destination
- * address and destination port are regarded as pertaining to the server---and vice versa if set
- * to {@code false}.
- * @return A {@code Conversation} initiated with ip:port for client and server according to the direction of the packet.
- */
- public static Conversation fromPcapPacket(PcapPacket pcapPacket, boolean clientIsSrc) {
- IpV4Packet ipPacket = pcapPacket.get(IpV4Packet.class);
- TcpPacket tcpPacket = pcapPacket.get(TcpPacket.class);
- String clientIp = clientIsSrc ? ipPacket.getHeader().getSrcAddr().getHostAddress() :
- ipPacket.getHeader().getDstAddr().getHostAddress();
- String srvIp = clientIsSrc ? ipPacket.getHeader().getDstAddr().getHostAddress() :
- ipPacket.getHeader().getSrcAddr().getHostAddress();
- int clientPort = clientIsSrc ? tcpPacket.getHeader().getSrcPort().valueAsInt() :
- tcpPacket.getHeader().getDstPort().valueAsInt();
- int srvPort = clientIsSrc ? tcpPacket.getHeader().getDstPort().valueAsInt() :
- tcpPacket.getHeader().getSrcPort().valueAsInt();
- return new Conversation(clientIp, clientPort, srvIp, srvPort);
- }
-
- /**
- * Constructs a new {@code Conversation}.
- * @param clientIp The IP of the host that is considered the client (i.e. the host that initiates the conversation)
- * in the conversation.
- * @param clientPort The port number used by the client for the conversation.
- * @param serverIp The IP of the host that is considered the server (i.e. is the responder) in the conversation.
- * @param serverPort The port number used by the server for the conversation.
- */
- public Conversation(String clientIp, int clientPort, String serverIp, int serverPort) {
- this.mClientIp = clientIp;
- this.mClientPort = clientPort;
- this.mServerIp = serverIp;
- this.mServerPort = serverPort;
- this.mPackets = new ArrayList<>();
- this.mTlsApplicationDataPackets = new ArrayList<>();
- this.mSeqNumbersClient = new HashSet<>();
- this.mSeqNumbersSrv = new HashSet<>();
- this.mSynPackets = new ArrayList<>();
- this.mFinPackets = new ArrayList<>();
- this.mRstPackets = new ArrayList<>();
- this.mApplicationData = false;
- }
-
- /**
- * Add a packet to the list of packets associated with this conversation.
- * @param packet The packet that is to be added to (associated with) this conversation.
- * @param ignoreRetransmissions Boolean value indicating if retransmissions should be ignored.
- * If set to {@code true}, {@code packet} will <em>not</em> be added to the
- * internal list of packets pertaining to this {@code Conversation}
- * <em>iff</em> the sequence number of {@code packet} was already
- * seen in a previous packet.
- */
- public void addPacket(PcapPacket packet, boolean ignoreRetransmissions) {
- // Precondition: verify that packet does indeed pertain to conversation.
- onAddPrecondition(packet);
- if (ignoreRetransmissions && isRetransmission(packet)) {
- // Packet is a retransmission. Ignore it.
- return;
- }
- // Select direction-dependent set of sequence numbers seen so far and update it with sequence number of new packet.
- addSeqNumber(packet);
- // Finally add packet to list of packets pertaining to this conversation.
- mPackets.add(packet);
- // Preserve order of packets in list: sort according to timestamp.
- if (mPackets.size() > 1 &&
- mPackets.get(mPackets.size()-1).getTimestamp().isBefore(mPackets.get(mPackets.size()-2).getTimestamp())) {
- Collections.sort(mPackets, (o1, o2) -> {
- if (o1.getTimestamp().isBefore(o2.getTimestamp())) { return -1; }
- else if (o2.getTimestamp().isBefore(o1.getTimestamp())) { return 1; }
- else { return 0; }
- });
- }
- // If TLS, inspect packet to see if it's a TLS Application Data packet, and if so add it to the list of TLS
- // Application Data packets.
- if (isTls()) {
- TcpPacket tcpPacket = packet.get(TcpPacket.class);
- Packet tcpPayload = tcpPacket.getPayload();
- if (tcpPayload == null) {
- return;
- }
- byte[] rawPayload = tcpPayload.getRawData();
- // The SSL record header is at the front of the payload and is 5 bytes long.
- // The SSL record header type field (the first byte) is set to 23 if it is an Application Data packet.
- if (rawPayload != null && rawPayload.length >= 5) {
- if (rawPayload[0] == 23) {
- mTlsApplicationDataPackets.add(packet);
- // Consider the following packet a data packet if this packet's size == MTU size 1448
- if (rawPayload.length >= 1448)
- mApplicationData = true;
- } else if (rawPayload[0] == 20) {
- // Do nothing for now - CHANGE_CIPHER_SPEC
- } else if (rawPayload[0] == 21) {
- // Do nothing for now - ALERT
- } else if (rawPayload[0] == 22) {
- // Do nothing for now - HANDSHAKE
- } else {
- // If it is TLS with payload, but rawPayload[0] != 23
- if (mApplicationData == true) {
- // It is a continuation of the previous packet if the previous packet reaches MTU size 1448 and
- // it is not either type 20, 21, or 22
- mTlsApplicationDataPackets.add(packet);
- if (rawPayload.length < 1448)
- mApplicationData = false;
- }
- }
- }
- }
- }
-
- /**
- * Get a list of packets pertaining to this {@code Conversation}.
- * The returned list is a read-only list.
- * @return the list of packets pertaining to this {@code Conversation}.
- */
- public List<PcapPacket> getPackets() {
- // Return read-only view to prevent external code from manipulating internal state (preserve invariant).
- return Collections.unmodifiableList(mPackets);
- }
-
- /**
- * Records a TCP SYN packet as pertaining to this conversation (adds it to the the internal list).
- * Attempts to add duplicate SYN packets will be ignored, and the caller is made aware of the attempt to add a
- * duplicate by the return value being {@code false}.
- *
- * @param synPacket A {@link PcapPacket} wrapping a TCP SYN packet.
- * @return {@code true} if the packet was successfully added to this {@code Conversation}, {@code false} otherwise.
- */
- public boolean addSynPacket(PcapPacket synPacket) {
- onAddPrecondition(synPacket);
- final IpV4Packet synPacketIpSection = synPacket.get(IpV4Packet.class);
- final TcpPacket synPacketTcpSection = synPacket.get(TcpPacket.class);
- if (synPacketTcpSection == null || !synPacketTcpSection.getHeader().getSyn()) {
- throw new IllegalArgumentException("Not a SYN packet.");
- }
- // We are only interested in recording one copy of the two SYN packets (one SYN packet in each direction), i.e.,
- // we want to discard retransmitted SYN packets.
- if (mSynPackets.size() >= 2) {
- return false;
- }
- // Check the set of recorded SYN packets to see if we have already recorded a SYN packet going in the same
- // direction as the packet given in the argument.
- boolean matchingPrevSyn = mSynPackets.stream().anyMatch(p -> {
- IpV4Packet pIp = p.get(IpV4Packet.class);
- TcpPacket pTcp = p.get(TcpPacket.class);
- boolean srcAddrMatch = synPacketIpSection.getHeader().getSrcAddr().getHostAddress().
- equals(pIp.getHeader().getSrcAddr().getHostAddress());
- boolean dstAddrMatch = synPacketIpSection.getHeader().getDstAddr().getHostAddress().
- equals(pIp.getHeader().getDstAddr().getHostAddress());
- boolean srcPortMatch = synPacketTcpSection.getHeader().getSrcPort().valueAsInt() ==
- pTcp.getHeader().getSrcPort().valueAsInt();
- boolean dstPortMatch = synPacketTcpSection.getHeader().getDstPort().valueAsInt() ==
- pTcp.getHeader().getDstPort().valueAsInt();
- return srcAddrMatch && dstAddrMatch && srcPortMatch && dstPortMatch;
- });
- if (matchingPrevSyn) {
- return false;
- }
- // Update direction-dependent set of sequence numbers and record/log packet.
- addSeqNumber(synPacket);
- return mSynPackets.add(synPacket);
-
- /*
- mSynPackets.stream().anyMatch(p -> {
- IpV4Packet pIp = p.get(IpV4Packet.class);
- TcpPacket pTcp = p.get(TcpPacket.class);
- boolean srcAddrMatch = synPacketIpSection.getHeader().getSrcAddr().getHostAddress().
- equals(pIp.getHeader().getSrcAddr().getHostAddress());
- boolean dstAddrMatch = synPacketIpSection.getHeader().getDstAddr().getHostAddress().
- equals(pIp.getHeader().getDstAddr().getHostAddress());
- boolean srcPortMatch = synPacketTcpSection.getHeader().getSrcPort().valueAsInt() ==
- pTcp.getHeader().getSrcPort().valueAsInt();
- boolean dstPortMatch = synPacketTcpSection.getHeader().getDstPort().value() ==
- pTcp.getHeader().getDstPort().value();
-
- boolean fourTupleMatch = srcAddrMatch && dstAddrMatch && srcPortMatch && dstPortMatch;
-
- boolean seqNoMatch = synPacketTcpSection.getHeader().getSequenceNumber() ==
- pTcp.getHeader().getSequenceNumber();
-
- if (fourTupleMatch && !seqNoMatch) {
- // If the four tuple that identifies the conversation matches, but the sequence number is different,
- // it means that this SYN packet is, in fact, an attempt to establish a **new** connection, and hence
- // the given packet is NOT part of this conversation, even though the ip:port combinations are (by
- // chance) selected such that they match this conversation.
- throw new IllegalArgumentException("Attempt to add SYN packet that belongs to a different conversation " +
- "(which is identified by the same four tuple as this conversation)");
- }
- return fourTupleMatch && seqNoMatch;
- });
- */
- }
-
- /**
- * Get a list of SYN packets pertaining to this {@code Conversation}.
- * The returned list is a read-only list.
- * @return the list of SYN packets pertaining to this {@code Conversation}.
- */
- public List<PcapPacket> getSynPackets() {
- return Collections.unmodifiableList(mSynPackets);
- }
-
- /**
- * Adds a TCP FIN packet to the list of TCP FIN packets associated with this conversation.
- * @param finPacket The TCP FIN packet that is to be added to (associated with) this conversation.
- */
- public void addFinPacket(PcapPacket finPacket) {
- // Precondition: verify that packet does indeed pertain to conversation.
- onAddPrecondition(finPacket);
- // TODO: should call addSeqNumber here?
- addSeqNumber(finPacket);
- mFinPackets.add(new FinAckPair(finPacket));
- }
-
- /**
- * Attempt to ACK any FIN packets held by this conversation.
- * @param ackPacket The ACK for a FIN previously added to this conversation.
- */
- public void attemptAcknowledgementOfFin(PcapPacket ackPacket) {
- // Precondition: verify that the packet pertains to this conversation.
- onAddPrecondition(ackPacket);
- // Mark unack'ed FIN(s) that this ACK matches as ACK'ed (there might be more than one in case of retransmissions..?)
- mFinPackets.replaceAll(finAckPair -> !finAckPair.isAcknowledged() && finAckPair.isCorrespondingAckPacket(ackPacket) ? new FinAckPair(finAckPair.getFinPacket(), ackPacket) : finAckPair);
- }
-
- /**
- * Retrieves an unmodifiable view of the list of {@link FinAckPair}s associated with this {@code Conversation}.
- * @return an unmodifiable view of the list of {@link FinAckPair}s associated with this {@code Conversation}.
- */
- public List<FinAckPair> getFinAckPairs() {
- return Collections.unmodifiableList(mFinPackets);
- }
-
- /**
- * Get if this {@code Conversation} is considered to have been gracefully shut down.
- * A {@code Conversation} has been gracefully shut down if it contains a FIN+ACK pair for both directions
- * (client to server, and server to client).
- * @return {@code true} if the connection has been gracefully shut down, false otherwise.
- */
- public boolean isGracefullyShutdown() {
- // The conversation has been gracefully shut down if we have recorded a FIN from both the client and the server which have both been ack'ed.
- return mFinPackets.stream().anyMatch(finAckPair -> finAckPair.isAcknowledged() && PcapPacketUtils.isSource(finAckPair.getFinPacket(), mClientIp, mClientPort)) &&
- mFinPackets.stream().anyMatch(finAckPair -> finAckPair.isAcknowledged() && PcapPacketUtils.isSource(finAckPair.getFinPacket(), mServerIp, mServerPort));
- }
-
- /**
- * Add a TCP segment for which the RST flag is set to this {@code Conversation}.
- * @param packet A {@link PcapPacket} wrapping a TCP segment pertaining to this {@code Conversation} for which the
- * RST flag is set.
- */
- public void addRstPacket(PcapPacket packet) {
- /*
- * TODO:
- * When now also keeping track of RST packets, should we also...?
- * 1) Prevent later packets from being added once a RST segment has been added?
- * 2) Extend 'isGracefullyShutdown()' to also consider RST segments, or add another method, 'isShutdown()' that
- * both considers FIN/ACK (graceful) as well as RST (abrupt/"ungraceful") shutdown?
- * 3) Should it be impossible to associate more than one RST segment with each Conversation?
- */
- onAddPrecondition(packet);
- TcpPacket tcpPacket = packet.get(TcpPacket.class);
- if (tcpPacket == null || !tcpPacket.getHeader().getRst()) {
- throw new IllegalArgumentException("not a RST packet");
- }
- mRstPackets.add(packet);
- }
-
- /**
- * Get the TCP segments pertaining to this {@code Conversation} for which it was detected that the RST flag is set.
- * @return the TCP segments pertaining to this {@code Conversation} for which it was detected that the RST flag is
- * set.
- */
- public List<PcapPacket> getRstPackets() {
- return Collections.unmodifiableList(mRstPackets);
- }
-
- // =========================================================================================================
- // We simply reuse equals and hashCode methods of String.class to be able to use this class as a key
- // in a Map.
-
- /**
- * <em>Note:</em> currently, equality is determined based on pairwise equality of the elements of the four tuple
- * ({@link #mClientIp}, {@link #mClientPort}, {@link #mServerIp}, {@link #mServerPort}) for {@code this} and
- * {@code obj}.
- * @param obj The object to test for equality with {@code this}.
- * @return {@code true} if {@code obj} is considered equal to {@code this} based on the definition of equality given above.
- */
- @Override
- public boolean equals(Object obj) {
- return obj instanceof Conversation && this.toString().equals(obj.toString());
- }
-
- @Override
- public int hashCode() {
- return toString().hashCode();
- }
- // =========================================================================================================
-
- @Override
- public String toString() {
- return String.format("%s:%d %s:%d", mClientIp, mClientPort, mServerIp, mServerPort);
- }
-
- /**
- * Invoke to verify that the precondition holds when a caller attempts to add a packet to this {@code Conversation}.
- * An {@link IllegalArgumentException} is thrown if the precondition is violated.
- * @param packet the packet to be added to this {@code Conversation}
- */
- private void onAddPrecondition(PcapPacket packet) {
- // Apply precondition to preserve class invariant: all packets in mPackets must match the 4 tuple that
- // defines the conversation.
- IpV4Packet ipPacket = Objects.requireNonNull(packet.get(IpV4Packet.class));
- // For now we only support TCP flows.
- TcpPacket tcpPacket = Objects.requireNonNull(packet.get(TcpPacket.class));
- String ipSrc = ipPacket.getHeader().getSrcAddr().getHostAddress();
- String ipDst = ipPacket.getHeader().getDstAddr().getHostAddress();
- int srcPort = tcpPacket.getHeader().getSrcPort().valueAsInt();
- int dstPort = tcpPacket.getHeader().getDstPort().valueAsInt();
- String clientIp, serverIp;
- int clientPort, serverPort;
- if (ipSrc.equals(mClientIp)) {
- clientIp = ipSrc;
- clientPort = srcPort;
- serverIp = ipDst;
- serverPort = dstPort;
- } else {
- clientIp = ipDst;
- clientPort = dstPort;
- serverIp = ipSrc;
- serverPort = srcPort;
- }
- if (!(clientIp.equals(mClientIp) && clientPort == mClientPort &&
- serverIp.equals(mServerIp) && serverPort == mServerPort)) {
- throw new IllegalArgumentException(
- String.format("Attempt to add packet that does not pertain to %s",
- Conversation.class.getSimpleName()));
- }
- }
-
- /**
- * <p>
- * Determines if the TCP packet contained in {@code packet} is a retransmission of a previously seen (logged)
- * packet.
- * </p>
- *
- * <b>
- * TODO:
- * the current implementation, which uses a set of previously seen sequence numbers, will consider a segment
- * with a reused sequence number---occurring as a result of sequence number wrap around for a very long-lived
- * connection---as a retransmission (and may therefore end up discarding it even though it is in fact NOT a
- * retransmission). Ideas?
- * </b>
- *
- * @param packet The packet.
- * @return {@code true} if {@code packet} was determined to be a retransmission, {@code false} otherwise.
- */
- public boolean isRetransmission(PcapPacket packet) {
- // Extract sequence number.
- int seqNo = packet.get(TcpPacket.class).getHeader().getSequenceNumber();
- switch (getDirection(packet)) {
- case CLIENT_TO_SERVER:
- return mSeqNumbersClient.contains(seqNo);
- case SERVER_TO_CLIENT:
- return mSeqNumbersSrv.contains(seqNo);
- default:
- throw new AssertionError(String.format("Unexpected value of enum '%s'",
- Direction.class.getSimpleName()));
- }
- }
-
- /**
- * <p>
- * Is this {@code Conversation} a TLS session?
- * </p>
- *
- * <em>Note: the current implementation simply examines the port number(s) for 443; it does <b>not</b> verify if the
- * application data is indeed encrypted.</em>
- *
- * @return {@code true} if this {@code Conversation} is interpreted as a TLS session, {@code false} otherwise.
- */
- public boolean isTls() {
- /*
- * TODO:
- * - may want to change this to be "return mServerPort == 443 || mClientPort == 443;" in order to also detect
- * TLS in those cases where it is not possible to correctly label who is the client and who is the server,
- * i.e., when the trace does not contain the SYN/SYNACK exchange.
- * - current implementation relies on the server using the conventional TLS port number; may instead want to
- * inspect the first 4 bytes of each potential TLS packet to see if they match the SSL record header.
- *
- * 08/31/18: Added unconvetional TLS ports used by WeMo plugs and LiFX bulb.
- * 09/20/18: Moved hardcoded ports to other class to allow other classes to query the set of TLS ports.
- */
- return TcpConversationUtils.isTlsPort(mServerPort);
- }
-
- /**
- * If this {@code Conversation} is backing a TLS session (i.e., if the value of {@link #isTls()} is {@code true}),
- * get the packets labeled as TLS Application Data packets. This is a subset of the full set of payload-carrying
- * packets (as returned by {@link #getPackets()}). An exception is thrown if this method is invoked on a
- * {@code Conversation} for which {@link #isTls()} returns {@code false}.
- *
- * @return A list containing exactly those packets that could be identified as TLS Application Data packets (through
- * inspecting of the SSL record header). The list may be empty, if no TLS application data packets have been
- * recorded for this {@code Conversation}.
- */
- public List<PcapPacket> getTlsApplicationDataPackets() {
- if (!isTls()) {
- throw new NoSuchElementException("cannot get TLS Application Data packets for non-TLS TCP conversation");
- }
- return Collections.unmodifiableList(mTlsApplicationDataPackets);
- }
-
- /**
- * Extracts the TCP sequence number from {@code packet} and adds it to the proper set of sequence numbers by
- * analyzing the direction of the packet.
- * @param packet A TCP packet (wrapped in a {@code PcapPacket}) that was added to this conversation and whose
- * sequence number is to be recorded as seen.
- */
- private void addSeqNumber(PcapPacket packet) {
- // Note: below check is redundant if client code is correct as the call to check the precondition should already
- // have been made by the addXPacket method that invokes this method. As such, the call below may be removed in
- // favor of speed, but the improvement will be minor, hence the added safety may be worth it.
- onAddPrecondition(packet);
- // Extract sequence number.
- int seqNo = packet.get(TcpPacket.class).getHeader().getSequenceNumber();
- // Determine direction of packet and add packet's sequence number to corresponding set of sequence numbers.
- switch (getDirection(packet)) {
- case CLIENT_TO_SERVER:
- // Client to server packet.
- mSeqNumbersClient.add(seqNo);
- break;
- case SERVER_TO_CLIENT:
- // Server to client packet.
- mSeqNumbersSrv.add(seqNo);
- break;
- default:
- throw new AssertionError(String.format("Unexpected value of enum '%s'",
- Direction.class.getSimpleName()));
- }
- }
-
- /**
- * Determine the direction of {@code packet}. An {@link IllegalArgumentException} is thrown if {@code packet} does
- * not pertain to this conversation.
- *
- * @param packet The packet whose direction is to be determined.
- * @return A {@link Direction} indicating the direction of the packet.
- */
- public Direction getDirection(PcapPacket packet) {
- IpV4Packet ipPacket = packet.get(IpV4Packet.class);
- String ipSrc = ipPacket.getHeader().getSrcAddr().getHostAddress();
- String ipDst = ipPacket.getHeader().getDstAddr().getHostAddress();
- // Determine direction of packet.
- if (ipSrc.equals(mClientIp) && ipDst.equals(mServerIp)) {
- // Client to server packet.
- return Direction.CLIENT_TO_SERVER;
- } else if (ipSrc.equals(mServerIp) && ipDst.equals(mClientIp)) {
- // Server to client packet.
- return Direction.SERVER_TO_CLIENT;
- } else {
- throw new IllegalArgumentException("getDirection: packet not related to " + getClass().getSimpleName());
- }
- }
-
- /**
- * Utility enum for expressing the direction of a packet pertaining to this {@code Conversation}.
- */
- public enum Direction {
-
- CLIENT_TO_SERVER {
- @Override
- public String toCompactString() {
- return "*";
- }
- },
- SERVER_TO_CLIENT {
- @Override
- public String toCompactString() {
- return "";
- }
- };
-
- /**
- * Get a compact string representation of this {@code Direction}.
- * @return a compact string representation of this {@code Direction}.
- */
- abstract public String toCompactString();
-
- }
-
-}
projects / pingpong.git / blobdiff