diff --git a/FTP/build.gradle b/FTP/build.gradle
new file mode 100644
index 0000000..b1a9381
--- /dev/null
+++ b/FTP/build.gradle
@@ -0,0 +1,26 @@
+plugins {
+ id 'java-library'
+}
+
+dependencies {
+ api 'org.apache.commons:commons-math3:3.6.1'
+
+ implementation 'com.google.guava:guava:23.0'
+
+ compile group: 'org.jetbrains', name: 'annotations', version: '15.0'
+ compile group: 'commons-io', name: 'commons-io', version: '2.6'
+
+ testCompile group: 'org.hamcrest', name: 'hamcrest-all', version: '1.3'
+ testCompile group: 'org.junit.jupiter', name: 'junit-jupiter-api', version: '5.1.0'
+ testCompile group: 'org.junit.jupiter', name: 'junit-jupiter-params', version: '5.0.0-M4'
+
+ testImplementation 'junit:junit:4.12'
+}
+
+repositories {
+ jcenter()
+}
+task wrapper(type: Wrapper) {
+ description = 'Generates gradlew[.bat] scripts'
+ gradleVersion = '4.6'
+}
diff --git a/FTP/gradle/wrapper/gradle-wrapper.jar b/FTP/gradle/wrapper/gradle-wrapper.jar
new file mode 100644
index 0000000..01b8bf6
Binary files /dev/null and b/FTP/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/FTP/gradle/wrapper/gradle-wrapper.properties b/FTP/gradle/wrapper/gradle-wrapper.properties
new file mode 100644
index 0000000..88f8762
--- /dev/null
+++ b/FTP/gradle/wrapper/gradle-wrapper.properties
@@ -0,0 +1,6 @@
+#Sun Apr 22 23:21:38 MSK 2018
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.6-all.zip
diff --git a/FTP/gradlew b/FTP/gradlew
new file mode 100755
index 0000000..cccdd3d
--- /dev/null
+++ b/FTP/gradlew
@@ -0,0 +1,172 @@
+#!/usr/bin/env sh
+
+##############################################################################
+##
+## Gradle start up script for UN*X
+##
+##############################################################################
+
+# Attempt to set APP_HOME
+# Resolve links: $0 may be a link
+PRG="$0"
+# Need this for relative symlinks.
+while [ -h "$PRG" ] ; do
+ ls=`ls -ld "$PRG"`
+ link=`expr "$ls" : '.*-> \(.*\)$'`
+ if expr "$link" : '/.*' > /dev/null; then
+ PRG="$link"
+ else
+ PRG=`dirname "$PRG"`"/$link"
+ fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS=""
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn () {
+ echo "$*"
+}
+
+die () {
+ echo
+ echo "$*"
+ echo
+ exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "`uname`" in
+ CYGWIN* )
+ cygwin=true
+ ;;
+ Darwin* )
+ darwin=true
+ ;;
+ MINGW* )
+ msys=true
+ ;;
+ NONSTOP* )
+ nonstop=true
+ ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+ if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+ # IBM's JDK on AIX uses strange locations for the executables
+ JAVACMD="$JAVA_HOME/jre/sh/java"
+ else
+ JAVACMD="$JAVA_HOME/bin/java"
+ fi
+ if [ ! -x "$JAVACMD" ] ; then
+ die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+ fi
+else
+ JAVACMD="java"
+ which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
+ MAX_FD_LIMIT=`ulimit -H -n`
+ if [ $? -eq 0 ] ; then
+ if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
+ MAX_FD="$MAX_FD_LIMIT"
+ fi
+ ulimit -n $MAX_FD
+ if [ $? -ne 0 ] ; then
+ warn "Could not set maximum file descriptor limit: $MAX_FD"
+ fi
+ else
+ warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
+ fi
+fi
+
+# For Darwin, add options to specify how the application appears in the dock
+if $darwin; then
+ GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
+fi
+
+# For Cygwin, switch paths to Windows format before running java
+if $cygwin ; then
+ APP_HOME=`cygpath --path --mixed "$APP_HOME"`
+ CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+ JAVACMD=`cygpath --unix "$JAVACMD"`
+
+ # We build the pattern for arguments to be converted via cygpath
+ ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
+ SEP=""
+ for dir in $ROOTDIRSRAW ; do
+ ROOTDIRS="$ROOTDIRS$SEP$dir"
+ SEP="|"
+ done
+ OURCYGPATTERN="(^($ROOTDIRS))"
+ # Add a user-defined pattern to the cygpath arguments
+ if [ "$GRADLE_CYGPATTERN" != "" ] ; then
+ OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
+ fi
+ # Now convert the arguments - kludge to limit ourselves to /bin/sh
+ i=0
+ for arg in "$@" ; do
+ CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
+ CHECK2=`echo "$arg"|egrep -c "^-"` ### Determine if an option
+
+ if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then ### Added a condition
+ eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
+ else
+ eval `echo args$i`="\"$arg\""
+ fi
+ i=$((i+1))
+ done
+ case $i in
+ (0) set -- ;;
+ (1) set -- "$args0" ;;
+ (2) set -- "$args0" "$args1" ;;
+ (3) set -- "$args0" "$args1" "$args2" ;;
+ (4) set -- "$args0" "$args1" "$args2" "$args3" ;;
+ (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
+ (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
+ (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
+ (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
+ (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
+ esac
+fi
+
+# Escape application args
+save () {
+ for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
+ echo " "
+}
+APP_ARGS=$(save "$@")
+
+# Collect all arguments for the java command, following the shell quoting and substitution rules
+eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
+
+# by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
+if [ "$(uname)" = "Darwin" ] && [ "$HOME" = "$PWD" ]; then
+ cd "$(dirname "$0")"
+fi
+
+exec "$JAVACMD" "$@"
diff --git a/FTP/gradlew.bat b/FTP/gradlew.bat
new file mode 100644
index 0000000..f955316
--- /dev/null
+++ b/FTP/gradlew.bat
@@ -0,0 +1,84 @@
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS=
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto init
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto init
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:init
+@rem Get command-line arguments, handling Windows variants
+
+if not "%OS%" == "Windows_NT" goto win9xME_args
+
+:win9xME_args
+@rem Slurp the command line arguments.
+set CMD_LINE_ARGS=
+set _SKIP=2
+
+:win9xME_args_slurp
+if "x%~1" == "x" goto execute
+
+set CMD_LINE_ARGS=%*
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega
diff --git a/FTP/settings.gradle b/FTP/settings.gradle
new file mode 100644
index 0000000..8af3acb
--- /dev/null
+++ b/FTP/settings.gradle
@@ -0,0 +1,2 @@
+rootProject.name = 'FTP'
+
diff --git a/FTP/src/main/java/FTPClient.java b/FTP/src/main/java/FTPClient.java
new file mode 100644
index 0000000..1a031cb
--- /dev/null
+++ b/FTP/src/main/java/FTPClient.java
@@ -0,0 +1,97 @@
+import org.apache.commons.io.IOUtils;
+import org.jetbrains.annotations.NotNull;
+
+import java.io.*;
+import java.net.Socket;
+import java.nio.file.FileAlreadyExistsException;
+
+/**
+ * This class provides methods to work with FTPServer. These are:
+ *
+ * {@link FTPClient#list(String)} -- prints all files in the target directory.
+ *
+ * {@link FTPClient#get(String, String)} -- downloads and saves file from the
+ * server to the target file.
+ */
+@SuppressWarnings({"unused", "WeakerAccess"})
+public class FTPClient {
+
+ private final static int BUF_SIZE = 2048;
+
+ @NotNull
+ final private DataOutputStream os;
+ @NotNull
+ final private DataInputStream is;
+
+ /**
+ * Creates new client, that connected to the FTPServer.
+ *
+ * @param url servers url.
+ * @param port port to connect.
+ * @throws IOException if any IOException occurred.
+ */
+ public FTPClient(final String url, final int port) throws IOException {
+ final Socket socket = new Socket(url, port);
+ os = new DataOutputStream(socket.getOutputStream());
+ is = new DataInputStream(socket.getInputStream());
+ }
+
+ /**
+ * Creates new client, that connected to the FTPServer.
+ *
+ * @param url servers url.
+ * @throws IOException if any IOException occurred.
+ */
+ public FTPClient(final String url) throws IOException {
+ this(url, FTPServer.DEFAULT_PORT);
+ }
+
+ /**
+ * Prints list of all files (including folders), inside the source folder.
+ *
+ * Also for every file prints whether the file is a directory or not.
+ *
+ * @param source target folder.
+ * @throws IOException if any IOException occurred.
+ */
+ public void list(@NotNull final String source) throws IOException {
+ os.writeInt(1);
+ os.writeUTF(source);
+ os.flush();
+
+ final int number = is.readInt();
+ System.out.println("Total number of files: " + number);
+ for (int i = 0; i < number; i++) {
+ final String name = is.readUTF();
+ final boolean isFolder = is.readBoolean();
+ final String isFolderString = isFolder ? "is a folder." : "is not a folder.";
+ System.out.println("\"" + name + "\" " + isFolderString);
+ }
+ }
+
+ /**
+ * Downloads file from the server to the file with specified name. If file with
+ * the given name already exists, FileAlreadyExistsException will be thrown.
+ *
+ * @param source target file.
+ * @param destination path, to save file.
+ * @throws IOException if any IOException occurred.
+ */
+ public void get(@NotNull final String source, @NotNull final String destination) throws IOException {
+ os.writeInt(2);
+ os.writeUTF(source);
+ os.flush();
+
+ final File file = new File(destination);
+ if (!file.createNewFile()) {
+ throw new FileAlreadyExistsException();
+ }
+ final byte[] buf = new byte[BUF_SIZE];
+ try (final FileOutputStream os = new FileOutputStream(file)) {
+ final long size = is.readLong();
+ IOUtils.copyLarge(is, os, 0, size);
+ }
+ }
+
+ private class FileAlreadyExistsException extends RuntimeException {}
+}
diff --git a/FTP/src/main/java/FTPServer.java b/FTP/src/main/java/FTPServer.java
new file mode 100644
index 0000000..ca54544
--- /dev/null
+++ b/FTP/src/main/java/FTPServer.java
@@ -0,0 +1,62 @@
+import abstractServer.AbstractBlockingServer;
+import abstractServer.Session;
+import org.jetbrains.annotations.NotNull;
+
+import java.io.IOException;
+import java.net.Socket;
+
+/**
+ * FTPServer class. Has factory init method and shutDown method. Also it is possible
+ * to track mistakes, that happened during server work.
+ *
+ * Server may accept a lot of clients and work with them in distinct thread by {@link FTPSession}
+ * class. In fact all possibilities of server are described in {@link FTPSession}.
+ *
+ * Server will shut down if any error occurred during it's work (not just in one created session).
+ **/
+@SuppressWarnings("unused")
+public class FTPServer extends AbstractBlockingServer {
+
+ @SuppressWarnings("WeakerAccess")
+ public final static int DEFAULT_PORT = 9995;
+
+ private FTPServer(final int port) throws IOException {
+ super(port);
+ }
+
+ private FTPServer() throws IOException {
+ this(DEFAULT_PORT);
+ }
+
+ @NotNull
+ @Override
+ protected Session newSession(final Socket socket, final int number) {
+ return new FTPSession(socket, number, this);
+ }
+
+ /**
+ * Creates new FTPServer on {@link FTPServer#DEFAULT_PORT} port.
+ *
+ * @return new FTPServer on default port.
+ * @throws IOException if IOException happened while creating new server.
+ */
+ @SuppressWarnings({"WeakerAccess", "UnusedReturnValue"})
+ public static FTPServer init() throws IOException {
+ return new FTPServer();
+ }
+
+ /**
+ * Creates new FTPServer on target port.
+ *
+ * @param port port to create server on.
+ * @return new FTPServer on default port.
+ * @throws IOException if IOException happened while creating new server.
+ */
+ public static FTPServer init(final int port) throws IOException {
+ return new FTPServer(port);
+ }
+
+ public static void main(final String[] args) throws IOException {
+ init();
+ }
+}
diff --git a/FTP/src/main/java/FTPSession.java b/FTP/src/main/java/FTPSession.java
new file mode 100644
index 0000000..f4059ba
--- /dev/null
+++ b/FTP/src/main/java/FTPSession.java
@@ -0,0 +1,82 @@
+import abstractServer.AbstractBlockingSession;
+import abstractServer.Server;
+import org.apache.commons.io.IOUtils;
+import org.jetbrains.annotations.NotNull;
+
+import java.io.*;
+import java.net.Socket;
+import java.util.Objects;
+
+class FTPSession extends AbstractBlockingSession {
+
+ private static final int BUF_SIZE = 2048;
+
+ FTPSession(@NotNull final Socket socket, final int id, final Server server) {
+ super(socket, id, server);
+ }
+
+ @Override
+ protected void processInput(@NotNull final DataInputStream is) throws IOException {
+ while (true) {
+ final int query = is.readInt();
+ final String path = is.readUTF();
+ switch (query) {
+ case 1:
+ addTask(() -> sendList(path));
+ break;
+ case 2:
+ addTask(() -> sendFile(path));
+ break;
+ case 3:
+ closeSession(null);
+ return;
+ default:
+ // do nothing, unknown command
+ }
+ }
+ }
+
+ private void sendList(@NotNull final String path) {
+ try (final ByteArrayOutputStream bos = new ByteArrayOutputStream(BUF_SIZE);
+ final DataOutputStream os = new DataOutputStream(bos)) {
+
+ final File target = new File(path);
+ if (!target.isDirectory()) {
+ os.writeInt(0);
+ } else {
+ os.writeInt(Objects.requireNonNull(target.listFiles()).length);
+ for (final File file : Objects.requireNonNull(target.listFiles())) {
+ os.writeUTF(file.getName());
+ os.writeBoolean(file.isDirectory());
+ }
+ }
+ sendToClient(bos.toByteArray());
+
+ } catch (@NotNull final IOException e) {
+ closeSession(e);
+ }
+ }
+
+ private void sendFile(@NotNull final String path) {
+ final File target = new File(path);
+ if (!target.isFile() || !target.canRead()) {
+ sendToClient(0);
+ return;
+ }
+ sendToClient(target.length());
+ final byte[] buf = new byte[BUF_SIZE];
+ try (final InputStream is = new FileInputStream(target)) {
+ int bytesRead;
+ while (true) {
+ bytesRead = is.read(buf);
+ if (bytesRead == -1) {
+ break;
+ }
+ sendToClient(buf, 0, bytesRead);
+ }
+
+ } catch (@NotNull final IOException e) {
+ closeSession(e);
+ }
+ }
+}
diff --git a/FTP/src/main/java/abstractServer/AbstractBlockingServer.java b/FTP/src/main/java/abstractServer/AbstractBlockingServer.java
new file mode 100644
index 0000000..0c654fe
--- /dev/null
+++ b/FTP/src/main/java/abstractServer/AbstractBlockingServer.java
@@ -0,0 +1,150 @@
+package abstractServer;
+
+import org.jetbrains.annotations.NotNull;
+
+import java.io.IOException;
+import java.net.ServerSocket;
+import java.net.Socket;
+import java.net.SocketException;
+import java.util.*;
+import java.util.concurrent.Executor;
+import java.util.concurrent.Executors;
+
+@SuppressWarnings("unused")
+public abstract class AbstractBlockingServer implements Server {
+
+ @NotNull
+ private final ServerSocket server;
+ private final int port;
+
+ @NotNull
+ private final Thread mainThread;
+
+ private volatile boolean ceaseWorking;
+ private volatile boolean serverClosed;
+
+ private final Set sessions = new TreeSet<>();
+ private int sessionsProcessed = 0;
+ private final List errors = new ArrayList<>();
+
+ private final Executor pool = Executors.newCachedThreadPool();
+
+ protected AbstractBlockingServer(final int port) throws IOException {
+ server = new ServerSocket(port);
+ this.port = port;
+ mainThread = new Thread(this::work);
+ mainThread.start();
+ }
+
+ /**
+ * The method shuts down server.
+ *
+ * Server will not accept connections anymore after this method was executed.
+ * Every present session will be closed.
+ *
+ * This is blocking method. You may interrupt this method for your own risk.
+ * In that case, it is not guaranteed that every port will be released by the time
+ * of the method end.
+ */
+ @Override
+ public synchronized void shutDown() {
+ if (ceaseWorking || serverClosed) {
+ return;
+ }
+ ceaseWorking = true;
+ try {
+ server.close();
+ mainThread.join();
+ } catch (@NotNull final IOException e) {
+ errors.add(e);
+ } catch (@NotNull final InterruptedException e) { // If we do not want to wait for shutdown
+ // do nothing
+ }
+
+ }
+
+ /**
+ * This method checks if any error occurred.
+ *
+ * @return true if any error occurred during work and false otherwise.
+ */
+ public boolean anyErrorOccurred() {
+ return errors.size() != 0;
+ }
+
+ /**
+ * Method to track all errors, occurred during work.
+ *
+ * @return list of occurred errors.
+ */
+ @NotNull
+ public List getErrors() {
+ return errors;
+ }
+
+ public Executor getPool() {
+ return pool;
+ }
+
+ private void work() {
+ System.out.println("Server was initialized on port " + port);
+
+ // working until error or shutdown
+ while (!ceaseWorking) {
+ final Socket socket;
+ try {
+ socket = server.accept(); // must be closed by session
+ final Session session = newSession(socket, sessionsProcessed++);
+ handleSession(session);
+ } catch (@NotNull final IOException e) {
+ if (e instanceof SocketException && ceaseWorking) {
+ break; // server was turned off
+ }
+ errors.add(e); // Shutdown if any error occurred
+ break;
+ }
+ }
+
+
+ // shutting down server if error happened
+ if (!server.isClosed()) {
+ try {
+ server.close();
+ } catch (@NotNull final IOException e) {
+ errors.add(e); // store all exceptions
+ }
+ }
+
+ // closing current connections
+ closeSessions();
+
+ serverClosed = true;
+ System.out.println("Server was shut down");
+ }
+
+ @Override
+ public void closeSession(@NotNull final Session session) {
+ sessions.remove(session);
+ session.close();
+ }
+
+ protected abstract Session newSession(final Socket socket, int number);
+
+ private void closeSessions() {
+ for (final Session session : sessions) {
+ session.close();
+ }
+ }
+
+ private void handleSession(@NotNull final Session session) {
+ sessions.add(session);
+ session.run(); // starts session
+ }
+}
+
+
+
+
+
+
+
diff --git a/FTP/src/main/java/abstractServer/AbstractBlockingSession.java b/FTP/src/main/java/abstractServer/AbstractBlockingSession.java
new file mode 100644
index 0000000..2c91ddc
--- /dev/null
+++ b/FTP/src/main/java/abstractServer/AbstractBlockingSession.java
@@ -0,0 +1,144 @@
+package abstractServer;
+
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.net.Socket;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.Executor;
+import java.util.concurrent.Executors;
+
+/**
+ * Abstract class to process one client connection.
+ *
+ * By default creates threads to process reading and writing. Every task from the client will
+ * be added to the ThreadPool.
+ *
+ * Also this class takes socket to work with as an input parameter, therefore this class
+ * must close the socket when it is not needed anymore (on {@link Session#close()} method call).
+ */
+public abstract class AbstractBlockingSession implements Session {
+
+ private final int id;
+ @NotNull
+ private final Socket socket;
+ private final Server server;
+
+ @NotNull
+ private final Executor executor;
+ private DataOutputStream os;
+
+ private final List errors = new ArrayList<>();
+
+ protected AbstractBlockingSession(final Socket socket, final int id, final Server server) {
+ this.socket = socket;
+ this.id = id;
+ this.server = server;
+ executor = Executors.newSingleThreadExecutor();
+
+ try {
+ os = new DataOutputStream(socket.getOutputStream());
+ } catch (@NotNull final IOException e) {
+ closeSession(e);
+ }
+ }
+
+ protected void closeSession(@Nullable final Exception e) {
+ if (e != null) {
+ errors.add(e);
+ }
+ server.closeSession(this);
+ }
+
+ // all docs inherited from Session interface
+ @Override
+ public void run() {
+ new Thread(this::processRead).start();
+ }
+
+ @Override
+ public int id() {
+ return id;
+ }
+
+ @Override
+ public void close() {
+ // we need two block in case of error happened in one of them
+ try {
+ os.close();
+ } catch (@NotNull final IOException e) {
+ errors.add(e);
+ e.printStackTrace();
+ }
+
+ try {
+ socket.close();
+ } catch (@NotNull final IOException e) {
+ errors.add(e);
+ e.printStackTrace();
+ }
+ }
+
+ @Override
+ public boolean anyErrorOccurred() {
+ return errors.size() != 0;
+ }
+
+ @NotNull
+ @Override
+ public List getErrors() {
+ return errors;
+ }
+
+ protected void sendToClient(@NotNull final byte[] buf) {
+ executor.execute(() -> {
+ try {
+ os.write(buf);
+ os.flush();
+ } catch (@NotNull final IOException e) {
+ closeSession(e);
+ }
+ });
+ }
+
+ protected void sendToClient(final long x) {
+ executor.execute(() -> {
+ try {
+ os.writeLong(x);
+ os.flush();
+ } catch (@NotNull final IOException e) {
+ closeSession(e);
+ }
+ });
+ }
+
+ @SuppressWarnings("SameParameterValue")
+ protected void sendToClient(@NotNull final byte[] buf, final int offset, final int length) {
+ executor.execute(() -> {
+ try {
+ os.write(buf, offset, length);
+ os.flush();
+ } catch (@NotNull final IOException e) {
+ closeSession(e);
+ }
+ });
+ }
+
+ private void processRead() {
+ try (final DataInputStream is = new DataInputStream(socket.getInputStream())) {
+ processInput(is);
+ } catch (@NotNull final IOException e) {
+ closeSession(e);
+ }
+ }
+
+ protected abstract void processInput(final DataInputStream is) throws IOException;
+
+ protected void addTask(final Runnable task) {
+ server.getPool().execute(task);
+ }
+}
diff --git a/FTP/src/main/java/abstractServer/Server.java b/FTP/src/main/java/abstractServer/Server.java
new file mode 100644
index 0000000..855bcfa
--- /dev/null
+++ b/FTP/src/main/java/abstractServer/Server.java
@@ -0,0 +1,23 @@
+package abstractServer;
+
+import java.util.concurrent.Executor;
+
+/**
+ * Server interface. Might have different architectures.
+ */
+public interface Server {
+
+ /**
+ * Turns off the server. It is required, that any implementation releases
+
+ * every port, used by server.
+ */
+ void shutDown();
+
+ /**
+ * Call this method to close one exact session.
+ */
+ void closeSession(Session session);
+
+ Executor getPool();
+}
diff --git a/FTP/src/main/java/abstractServer/Session.java b/FTP/src/main/java/abstractServer/Session.java
new file mode 100644
index 0000000..67ee0ed
--- /dev/null
+++ b/FTP/src/main/java/abstractServer/Session.java
@@ -0,0 +1,58 @@
+package abstractServer;
+
+import org.jetbrains.annotations.NotNull;
+
+import java.io.Closeable;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.Executor;
+
+/**
+ * This interface provides session methods to work with one exact client.
+ */
+@SuppressWarnings("unused")
+public interface Session extends Comparable, Closeable {
+
+ /**
+ * Id is required to implement comparable method, therefore server might
+ * be able to store sessions in set.
+ *
+ * @return session id
+ */
+ int id();
+
+ /**
+ * The method must be used to close all resources, such as sockets, Readers e.t.c.
+ */
+ @Override
+ void close();
+
+ @Override
+ default int compareTo(@NotNull final Session o) {
+ return id() - o.id();
+ }
+
+ /**
+ * Starts to process the session. For example, this method might start reading
+ * and writing threads.
+ */
+ void run();
+
+ /**
+ * This method checks if any error occurred.
+ *
+ * @return true if any error occurred during work and false otherwise.
+ */
+ default boolean anyErrorOccurred() {
+ return false;
+ }
+
+ /**
+ * Method to track all errors, occurred during work.
+ *
+ * @return list of occurred errors.
+ */
+ default List getErrors() {
+ return Collections.emptyList();
+ }
+}
diff --git a/FTP/src/test/java/FTPClientTest.java b/FTP/src/test/java/FTPClientTest.java
new file mode 100644
index 0000000..36678c3
--- /dev/null
+++ b/FTP/src/test/java/FTPClientTest.java
@@ -0,0 +1,89 @@
+import abstractServer.Utils;
+import org.apache.commons.io.FileUtils;
+import org.jetbrains.annotations.NotNull;
+import org.junit.jupiter.api.Test;
+
+import java.io.ByteArrayOutputStream;
+import java.io.File;
+import java.io.IOException;
+import java.io.PrintStream;
+import java.util.Arrays;
+import java.util.Map;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.*;
+
+
+class FTPClientTest {
+
+ @Test
+ void testListEmpty() throws IOException {
+ Utils.clear();
+ testListWithContent(Utils.map());
+ testListWithContent(Utils.map("file1", false));
+ testListWithContent(Utils.map("file1", true));
+ testListWithContent(Utils.map("file1", true, "file2", false));
+ }
+
+ private void testListWithContent(@NotNull final Map files) throws IOException {
+ final FTPServer server = FTPServer.init();
+ final FTPClient client = new FTPClient("localhost", FTPServer.DEFAULT_PORT);
+ try {
+ Thread.sleep(100);
+ } catch (@NotNull final InterruptedException e) {
+ // do nothing
+ }
+
+ for (final Map.Entry entry : files.entrySet()) {
+ if (entry.getValue()) {
+ Utils.createFile(entry.getKey() + File.separator + "dummy");
+ } else {
+ Utils.createFile(entry.getKey());
+ }
+ }
+
+ final ByteArrayOutputStream os = new ByteArrayOutputStream();
+
+ final PrintStream old = System.out;
+ System.setOut(new PrintStream(os));
+ client.list(Utils.sourceDir);
+
+ final StringBuilder answer = new StringBuilder("Total number of files: " + files.size() + "\n");
+ for (final Map.Entry entry : files.entrySet()) {
+ final String isFolderString = entry.getValue() ? "is a folder." : "is not a folder.";
+ answer.append("\"").append(entry.getKey())
+ .append("\" ").append(isFolderString).append('\n');
+ }
+ assertThat(Arrays.asList(os.toString().split("\n")),
+ containsInAnyOrder(answer.toString().split("\n")));
+
+ System.setOut(old);
+ Utils.clear();
+ server.shutDown();
+ }
+
+ @Test
+ void testGet() throws IOException {
+ Utils.clear();
+ testGetWithContent();
+ testGetWithContent("hello");
+ testGetWithContent("hello", "one");
+ testGetWithContent("hello", "hello");
+ }
+
+ private void testGetWithContent(final String... content) throws IOException {
+ final FTPServer server = FTPServer.init();
+ final FTPClient client = new FTPClient("localhost", FTPServer.DEFAULT_PORT);
+
+ Utils.createFile("file", content);
+
+ client.get(Utils.getFileName("file"), "tmp.txt");
+
+ FileUtils.contentEquals(new File(Utils.getFileName("file")), new File("tmp.txt"));
+
+ Utils.deleteFile("tmp.txt");
+ Utils.clear();
+ server.shutDown();
+ }
+
+}
\ No newline at end of file
diff --git a/FTP/src/test/java/abstractServer/AbstractBlockingServerTest.java b/FTP/src/test/java/abstractServer/AbstractBlockingServerTest.java
new file mode 100644
index 0000000..4f8214b
--- /dev/null
+++ b/FTP/src/test/java/abstractServer/AbstractBlockingServerTest.java
@@ -0,0 +1,97 @@
+package abstractServer;
+
+import abstractServer.dummies.DummyClient;
+import abstractServer.dummies.DummyException;
+import abstractServer.dummies.DummyServer;
+import abstractServer.dummies.DummySession;
+import org.jetbrains.annotations.NotNull;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.*;
+import static org.hamcrest.core.Every.everyItem;
+import static org.hamcrest.core.Is.is;
+
+class AbstractBlockingServerTest {
+
+ @Test
+ void initAndShutDown() throws IOException {
+ DummyServer server = DummyServer.init();
+
+ for (int i = 0; i < 5; i++) {
+ server.shutDown();
+ server = DummyServer.init();
+ assertThat(server.anyErrorOccurred(), is(false));
+ }
+
+ server.shutDown();
+ }
+
+ @Test
+ void testMessages() throws IOException {
+ final DummyServer server = DummyServer.init();
+
+ for (int i = 0; i < 5; i++) {
+ new DummyClient().sendCommands(42, 17, 46, 14, 22, 134);
+ }
+
+ try {
+ Thread.sleep(1000);
+ } catch (@NotNull final InterruptedException e) {
+ // just waiting...
+ }
+
+ assertThat(server.anyErrorOccurred(), is(false));
+ assertThat(server.getErrors(), is(empty()));
+ assertThat(server.session().stream()
+ .map(DummySession::lines).collect(Collectors.toList()),
+ everyItem(is(Utils.list("42", "17", "46", "14", "22", "134"))));
+
+ assertThat(server.session().stream()
+ .map(DummySession::getErrors).collect(Collectors.toList()),
+ everyItem(is(empty())));
+
+
+ server.shutDown();
+ }
+
+ @Test
+ void testCloseSession() throws IOException {
+ final DummyServer server = DummyServer.init();
+
+ for (int i = 0; i < 3; i++) {
+ new DummyClient().sendCommands(-2);
+ }
+
+ try {
+ Thread.sleep(1000);
+ } catch (@NotNull final InterruptedException e) {
+ // just waiting...
+ }
+
+ assertThat(server.anyErrorOccurred(), is(false));
+ assertThat(server.getErrors(), is(empty()));
+ assertThat(server.session().stream().map(DummySession::getErrors)
+ .collect(Collectors.toList()),
+ everyItem(everyItem(is(instanceOf(DummyException.class)))));
+ assertThat(server.session().stream().map(DummySession::getErrors)
+ .collect(Collectors.toList()),
+ everyItem(iterableWithSize(1)));
+
+ server.shutDown();
+ }
+
+ @Test
+ void testAnswer() throws IOException {
+ final DummyServer server = DummyServer.init();
+
+ assertThat(new DummyClient().sendAnswerIntCommand(), is(42));
+
+ server.shutDown();
+ }
+
+}
\ No newline at end of file
diff --git a/FTP/src/test/java/abstractServer/Utils.java b/FTP/src/test/java/abstractServer/Utils.java
new file mode 100644
index 0000000..f1fcf21
--- /dev/null
+++ b/FTP/src/test/java/abstractServer/Utils.java
@@ -0,0 +1,71 @@
+package abstractServer;
+
+import org.jetbrains.annotations.NotNull;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.util.*;
+
+@SuppressWarnings({"WeakerAccess", "unused"})
+public class Utils {
+
+ public static final String sourceDir = "tempDir";
+
+ @NotNull
+ @SuppressWarnings("ResultOfMethodCallIgnored")
+ public static File createFile(final String name, @NotNull final String... lines) throws IOException {
+ final File file = new File(getFileName(name));
+ new File(file.getParent()).mkdirs();
+ file.createNewFile();
+
+ try (final PrintWriter writer = new PrintWriter(file)) {
+ for (final String line : lines) {
+ writer.append(line).append('\n');
+ }
+ }
+ return file;
+ }
+
+ @SuppressWarnings("ResultOfMethodCallIgnored")
+ public static void deleteFile(@NotNull final String name) {
+ final File file = new File(name);
+ if (!file.isDirectory()) {
+ file.delete();
+ } else {
+ //noinspection ConstantConditions
+ for (final File inner : file.listFiles()) {
+ deleteFile(inner.getAbsolutePath());
+ }
+ file.delete();
+ }
+ }
+
+ public static void clear() {
+ deleteFile(sourceDir);
+ }
+
+ public static String getFileName(final String name) {
+ return sourceDir + File.separator + name;
+ }
+
+ @NotNull
+ public static File createTemporaryFile(final String proxy, final String... lines) throws IOException {
+ final File file = createFile(proxy, lines);
+ file.deleteOnExit();
+ return file;
+ }
+
+ @SafeVarargs
+ public static List list(final T... values) {
+ return Arrays.asList(values);
+ }
+
+ public static Map map(final Object... elements) {
+ final Map result = new TreeMap<>();
+ for (int i = 0; i < elements.length; i++) {
+ result.put((String) elements[i], (Boolean) elements[++i]);
+ }
+ return result;
+ }
+}
\ No newline at end of file
diff --git a/FTP/src/test/java/abstractServer/dummies/DummyClient.java b/FTP/src/test/java/abstractServer/dummies/DummyClient.java
new file mode 100644
index 0000000..1337d69
--- /dev/null
+++ b/FTP/src/test/java/abstractServer/dummies/DummyClient.java
@@ -0,0 +1,37 @@
+package abstractServer.dummies;
+
+import org.jetbrains.annotations.NotNull;
+
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.net.Socket;
+
+public class DummyClient {
+
+ @NotNull
+ private final DataOutputStream os;
+ @NotNull
+ private final DataInputStream is;
+
+ public DummyClient() throws IOException {
+ final @NotNull Socket socket = new Socket("localhost", DummyServer.DEFAULT_PORT);
+ os = new DataOutputStream(socket.getOutputStream());
+ is = new DataInputStream(socket.getInputStream());
+ }
+
+ public void sendCommands(@NotNull final int... commands) throws IOException {
+ for (final int cmd : commands) {
+ os.writeInt(cmd);
+ os.flush();
+ }
+ }
+
+ public int sendAnswerIntCommand() throws IOException {
+ os.writeInt(1);
+ os.flush();
+
+ return is.readInt();
+ }
+
+}
diff --git a/FTP/src/test/java/abstractServer/dummies/DummyException.java b/FTP/src/test/java/abstractServer/dummies/DummyException.java
new file mode 100644
index 0000000..dd0b1ce
--- /dev/null
+++ b/FTP/src/test/java/abstractServer/dummies/DummyException.java
@@ -0,0 +1,5 @@
+package abstractServer.dummies;
+
+public class DummyException extends Exception {
+
+}
diff --git a/FTP/src/test/java/abstractServer/dummies/DummyServer.java b/FTP/src/test/java/abstractServer/dummies/DummyServer.java
new file mode 100644
index 0000000..323ce1e
--- /dev/null
+++ b/FTP/src/test/java/abstractServer/dummies/DummyServer.java
@@ -0,0 +1,42 @@
+package abstractServer.dummies;
+
+import abstractServer.AbstractBlockingServer;
+import abstractServer.Session;
+import org.jetbrains.annotations.NotNull;
+
+import java.io.IOException;
+import java.net.Socket;
+import java.util.ArrayList;
+import java.util.List;
+
+public class DummyServer extends AbstractBlockingServer {
+
+ @SuppressWarnings("WeakerAccess")
+ public final static int DEFAULT_PORT = 9925;
+
+ @NotNull
+ private final List sessionList = new ArrayList<>();
+
+ private DummyServer(final int port) throws IOException {
+ super(port);
+ }
+
+ @NotNull
+ @Override
+ protected Session newSession(final Socket socket, final int number) {
+ final DummySession session = new DummySession(socket, number, this);
+ sessionList.add(session);
+ return session;
+ }
+
+ @NotNull
+ public List session() {
+ return sessionList;
+ }
+
+ public static DummyServer init() throws IOException {
+ return new DummyServer(DEFAULT_PORT);
+ }
+
+
+}
diff --git a/FTP/src/test/java/abstractServer/dummies/DummySession.java b/FTP/src/test/java/abstractServer/dummies/DummySession.java
new file mode 100644
index 0000000..88458c3
--- /dev/null
+++ b/FTP/src/test/java/abstractServer/dummies/DummySession.java
@@ -0,0 +1,58 @@
+package abstractServer.dummies;
+
+import abstractServer.AbstractBlockingSession;
+import abstractServer.Server;
+import org.jetbrains.annotations.NotNull;
+
+import java.io.ByteArrayOutputStream;
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.net.Socket;
+import java.util.ArrayList;
+import java.util.List;
+
+public class DummySession extends AbstractBlockingSession {
+
+ private final List lines = new ArrayList<>();
+
+ DummySession(@NotNull final Socket socket, final int id, final Server server) {
+ super(socket, id, server);
+ }
+
+ @Override
+ protected void processInput(@NotNull final DataInputStream is) throws IOException {
+ while (true) {
+ final int cmd = is.readInt();
+ switch (cmd) {
+ case -1:
+ closeSession(null);
+ return;
+ case -2:
+ closeSession(new DummyException());
+ return;
+ case 1:
+ sendNumber(42);
+ break;
+ default:
+ lines.add(String.valueOf(cmd));
+ break;
+ }
+ }
+ }
+
+ @SuppressWarnings("SameParameterValue")
+ private void sendNumber(final int x) throws IOException {
+ final ByteArrayOutputStream bos = new ByteArrayOutputStream(1000);
+ final DataOutputStream os = new DataOutputStream(bos);
+
+ os.writeInt(x);
+
+ sendToClient(bos.toByteArray());
+ }
+
+ @NotNull
+ public List lines() {
+ return lines;
+ }
+}