Inital commit

.gitignore

@@ -0,0 +1,3 @@
+.gradle
+.idea
+build/

build.gradle

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+plugins {
+    id 'java'
+}
+
+group 'ru.redguy'
+version '1.0'
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+
+}

gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,5 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.3-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

gradlew

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+#!/usr/bin/env sh
+
+#
+# Copyright 2015 the original author or authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+##############################################################################
+##
+##  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 "$0"`
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn () {
+    echo "$*"
+}
+
+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 or MSYS, switch paths to Windows format before running java
+if [ "$cygwin" = "true" -o "$msys" = "true" ] ; 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=`expr $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"
+
+exec "$JAVACMD" "$@"

gradlew.bat

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+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
+@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 Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@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="-Xmx64m" "-Xms64m"
+
+@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

settings.gradle

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+rootProject.name = 'TFTPServer'
+

src/main/java/ru/redguy/tftpserver/CheckSum.java

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+package ru.redguy.tftpserver;
+
+import java.io.FileInputStream;
+import java.security.MessageDigest;
+
+
+public class CheckSum {
+	static String getChecksum(String fileName) {
+		StringBuffer sb = new StringBuffer("");
+		try {
+			String datafile = fileName;
+			//use SHA1 to calculate checksum
+			MessageDigest md = MessageDigest.getInstance("SHA1");
+			FileInputStream fis = new FileInputStream(datafile);
+			byte[] dataBytes = new byte[1024];
+
+			int nread = 0;
+
+			while ((nread = fis.read(dataBytes)) != -1) {
+				md.update(dataBytes, 0, nread);
+			}
+			fis.close();
+
+			byte[] mdbytes = md.digest();
+
+			// convert the byte to hex format
+			for (int i = 0; i < mdbytes.length; i++) {
+				sb.append(Integer.toString((mdbytes[i] & 0xff) + 0x100, 16).substring(1));
+			}
+
+		} catch (Exception e){System.out.println("Generate Checksum Failed: "+e.getMessage());}
+		
+		return sb.toString();
+	}
+	}

src/main/java/ru/redguy/tftpserver/ErrorEvent.java

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+package ru.redguy.tftpserver;
+
+public interface ErrorEvent {
+    public void onPacketReceiveException(Exception exception);
+    public void onPacketReadException(Exception exception);
+    public void onPacketWriteException(Exception exception);
+    public void onClientReadException(Exception exception, TFTPread tftPread);
+    public void onClientWriteException(Exception exception, TFTPwrite tftPwrite);
+}

src/main/java/ru/redguy/tftpserver/TFTPServer.java

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+package ru.redguy.tftpserver;
+
+import java.net.*;
+import java.io.*;
+
+public class TFTPServer {
+
+	private DatagramSocket socket;
+	private Runner runner;
+	private Thread thread;
+	private ErrorEvent errorEvent;
+
+	public void start() throws SocketException {
+		start(69);
+	}
+
+	public void start(int port) throws SocketException {
+		socket = new DatagramSocket(port);
+		runner = new Runner(socket,this);
+		thread = new Thread(runner);
+		thread.setDaemon(true);
+		thread.start();
+	}
+
+	public void start(String host, int port) throws UnknownHostException, SocketException {
+		socket = new DatagramSocket(port,InetAddress.getByName(host));
+		runner = new Runner(socket,this);
+		thread.setDaemon(true);
+		thread.start();
+	}
+
+	public int getPort() {
+		return socket.getLocalPort();
+	}
+
+	public void stop() {
+		thread.interrupt();
+	}
+
+	public void onError(ErrorEvent event) {
+		this.errorEvent = event;
+	}
+
+	static class Runner implements Runnable {
+
+		DatagramSocket datagramSocket;
+		TFTPServer server;
+		boolean run = true;
+
+		public Runner(DatagramSocket socket,TFTPServer server) {
+			this.datagramSocket = socket;
+			this.server = server;
+		}
+
+		public void stop() {
+			run = false;
+		}
+
+		@Override
+		public void run() {
+			while (run) {
+				TFTPpacket in = null;
+				try {
+					in = TFTPpacket.receive(datagramSocket);
+				} catch (IOException e) {
+					server.errorEvent.onPacketReceiveException(e);
+				}
+
+				if (in instanceof TFTPread) {
+					try {
+						TFTPserverRRQ r = new TFTPserverRRQ((TFTPread) in, server.errorEvent);
+					} catch (TftpException e) {
+						server.errorEvent.onPacketReadException(e);
+					}
+				}
+
+				else if (in instanceof TFTPwrite) {
+					try {
+						TFTPserverWRQ w = new TFTPserverWRQ((TFTPwrite) in, server.errorEvent);
+					} catch (TftpException e) {
+						server.errorEvent.onPacketWriteException(e);
+					}
+				}
+			}
+		}
+	}
+}

src/main/java/ru/redguy/tftpserver/TFTPpacket.java

@@ -0,0 +1,219 @@
+package ru.redguy.tftpserver;
+
+import java.net.*;
+import java.io.*;
+
+class TftpException extends Exception {
+	public TftpException() {
+		super();
+	}
+	public TftpException(String s) {
+		super(s);
+	}
+}
+//////////////////////////////////////////////////////////////////////////////
+//GENERAL packet: define the packet structure, necessary members and methods// 
+//of TFTP packet. To be extended by other specific packet(read, write, etc) //
+//////////////////////////////////////////////////////////////////////////////
+public class TFTPpacket {
+
+  // TFTP constants
+  public static int tftpPort = 69;
+  public static int maxTftpPakLen=516;
+  public static int maxTftpData=512;
+
+  // Tftp opcodes
+  protected static final short tftpRRQ=1;
+  protected static final short tftpWRQ=2;
+  protected static final short tftpDATA=3;
+  protected static final short tftpACK=4;
+  protected static final short tftpERROR=5;
+
+  // Packet Offsets
+  protected static final int opOffset=0;
+
+  protected static final int fileOffset=2;
+
+  protected static final int blkOffset=2;
+  protected static final int dataOffset=4;
+
+  protected static final int numOffset=2;
+  protected static final int msgOffset=4;
+
+  // The actual packet for UDP transfer
+  protected byte [] message;
+  protected int length;
+
+  // Address info (required for replies)
+  protected InetAddress host;
+  protected int port;
+
+  // Constructor 
+  public TFTPpacket() {
+    message=new byte[maxTftpPakLen]; 
+    length=maxTftpPakLen; 
+  } 
+
+  // Methods to receive packet and convert it to yhe right type(data/ack/read/...)
+  public static TFTPpacket receive(DatagramSocket sock) throws IOException {
+    TFTPpacket in=new TFTPpacket(), retPak=new TFTPpacket();
+    //receive data and put them into in.message
+    DatagramPacket inPak = new DatagramPacket(in.message,in.length);
+    sock.receive(inPak); 
+    
+    //Check the opcode in message, then cast the message into the corresponding type
+    switch (in.get(0)) {
+      case tftpRRQ:
+    	  retPak=new TFTPread();
+        break;
+      case tftpWRQ:
+    	  retPak=new TFTPwrite();
+        break;
+      case tftpDATA:
+    	  retPak=new TFTPdata();
+        break;
+      case tftpACK:
+    	  retPak=new TFTPack();
+        break;
+      case tftpERROR:
+    	  retPak=new TFTPerror();
+        break;
+    }
+    retPak.message=in.message;
+    retPak.length=inPak.getLength();
+    retPak.host=inPak.getAddress();
+    retPak.port=inPak.getPort();
+
+    return retPak;
+  }
+  
+  //Method to send packet
+  public void send(InetAddress ip, int port, DatagramSocket s) throws IOException {
+    s.send(new DatagramPacket(message,length,ip,port));
+  }
+
+  // DatagramPacket like methods
+  public InetAddress getAddress() {
+    return host;
+  }
+
+  public int getPort() {
+    return port;
+  }
+
+  public int getLength() {
+    return length;
+  }
+
+  // Methods to put opcode, blkNum, error code into the byte array 'message'. 
+  protected void put(int at, short value) {
+    message[at++] = (byte)(value >>> 8);  // first byte
+    message[at] = (byte)(value % 256);    // last byte
+  }
+
+  @SuppressWarnings("deprecation")
+  //Put the filename and mode into the 'message' at 'at' follow by byte "del"
+  protected void put(int at, String value, byte del) {
+    value.getBytes(0, value.length(), message, at);
+    message[at + value.length()] = del;
+  }
+
+  protected int get(int at) {
+    return (message[at] & 0xff) << 8 | message[at+1] & 0xff;
+  }
+
+  protected String get (int at, byte del) {
+    StringBuffer result = new StringBuffer();
+    while (message[at] != del) result.append((char)message[at++]);
+    return result.toString();
+  }
+}
+
+////////////////////////////////////////////////////////
+//DATA packet: put the right code in the message; read// 
+//file for sending; write file after receiving        //
+////////////////////////////////////////////////////////
+final class TFTPdata extends TFTPpacket {
+
+	// Constructors
+	protected TFTPdata() {}
+	public TFTPdata(int blockNumber, FileInputStream in) throws IOException {
+		this.message = new byte[maxTftpPakLen];
+		// manipulate message
+		this.put(opOffset, tftpDATA);
+		this.put(blkOffset, (short) blockNumber);
+		// read the file into packet and calculate the entire length
+		length = in.read(message, dataOffset, maxTftpData) + 4;
+	}
+
+	// Accessors
+
+	public int blockNumber() {
+		return this.get(blkOffset);
+	}
+
+	/*
+	 * public void data(byte[] buffer) { buffer = new byte[length-4];
+	 * 
+	 * for (int i=0; i<length-4; i++) buffer[i]=message[i+dataOffset]; }
+	 */
+	
+	// File output
+	public int write(FileOutputStream out) throws IOException {
+		out.write(message, dataOffset, length - 4);
+
+		return (length - 4);
+	}
+}
+
+/////////////////////////////////////////////////////////
+//ERROR packet: put the right codes and error messages // 
+//in the 'message'                                     //
+/////////////////////////////////////////////////////////
+class TFTPerror extends TFTPpacket {
+
+	// Constructors
+	protected TFTPerror() {
+	}
+	//Generate error packet
+	public TFTPerror(int number, String message) {
+		length = 4 + message.length() + 1;
+		this.message = new byte[length];
+		put(opOffset, tftpERROR);
+		put(numOffset, (short) number);
+		put(msgOffset, message, (byte) 0);
+	}
+
+	// Accessors
+	public int number() {
+		return this.get(numOffset);
+	}
+	public String message() {
+		return this.get(msgOffset, (byte) 0);
+	}
+}
+
+/////////////////////////////////////////////////////////
+//ACK packet: put the right opcode and block number in // 
+//the 'message'                                        //
+/////////////////////////////////////////////////////////
+final class TFTPack extends TFTPpacket {
+
+	// Constructors
+	protected TFTPack() {
+	}
+	//Generate ack packet
+	public TFTPack(int blockNumber) {
+		length = 4;
+		this.message = new byte[length];
+		put(opOffset, tftpACK);
+		put(blkOffset, (short) blockNumber);
+	}
+
+	// Accessors
+	public int blockNumber() {
+		return this.get(blkOffset);
+	}
+}
+
+

src/main/java/ru/redguy/tftpserver/TFTPread.java

@@ -0,0 +1,34 @@
+package ru.redguy.tftpserver;
+
+/////////////////////////////////////////////////////////
+//READ packet: put the right opcode and filename, mode //
+//in the 'message'                                     //
+/////////////////////////////////////////////////////////
+public final class TFTPread extends TFTPpacket {
+
+
+    // Constructors
+    protected TFTPread() {
+    }
+
+    //specify the filename and transfer mode
+    public TFTPread(String filename, String dataMode) {
+        length = 2 + filename.length() + 1 + dataMode.length() + 1;
+        message = new byte[length];
+
+        put(opOffset, tftpRRQ);
+        put(fileOffset, filename, (byte) 0);
+        put(fileOffset + filename.length() + 1, dataMode, (byte) 0);
+    }
+
+// Accessors
+
+    public String fileName() {
+        return this.get(fileOffset, (byte) 0);
+    }
+
+    public String requestType() {
+        String fname = fileName();
+        return this.get(fileOffset + fname.length() + 1, (byte) 0);
+    }
+}

src/main/java/ru/redguy/tftpserver/TFTPserverRRQ.java

@@ -0,0 +1,97 @@
+package ru.redguy.tftpserver;
+
+import java.net.*;
+import java.io.*;
+
+
+class TFTPserverRRQ extends Thread {
+
+	protected DatagramSocket sock;
+	protected InetAddress host;
+	protected int port;
+	protected FileInputStream source;
+	protected TFTPpacket req;
+	protected int timeoutLimit=5;
+	protected String fileName;
+
+	// initialize read request
+	public TFTPserverRRQ(TFTPread request, ErrorEvent event) throws TftpException {
+		try {
+			req = request;
+			//open new socket with random port num for tranfer
+			sock = new DatagramSocket();
+			sock.setSoTimeout(1000);
+			fileName = request.fileName();
+
+			host = request.getAddress();
+			port = request.getPort();
+			
+			//create file object in parent folder
+			File srcFile = new File(fileName);
+			/*System.out.println("procce checking");*/
+			//check file
+			if (srcFile.exists() && srcFile.isFile() && srcFile.canRead()) {
+				source = new FileInputStream(srcFile);
+				this.start(); //open new thread for transfer
+			} else
+				throw new TftpException("access violation");
+
+		} catch (Exception e) {
+			TFTPerror ePak = new TFTPerror(1, e.getMessage()); // error code 1
+			try {
+				ePak.send(host, port, sock);
+			} catch (Exception f) {
+			}
+
+			event.onClientReadException(e,request);
+		}
+	}
+	//everything is fine, open new thread to transfer file
+	public void run() {
+		int bytesRead = TFTPpacket.maxTftpPakLen;
+		// handle read request
+		if (req instanceof TFTPread) {
+			try {
+				for (int blkNum = 1; bytesRead == TFTPpacket.maxTftpPakLen; blkNum++) {
+					TFTPdata outPak = new TFTPdata(blkNum, source);
+					/*System.out.println("send block no. " + outPak.blockNumber()); */
+					bytesRead = outPak.getLength();
+					/*System.out.println("bytes sent:  " + bytesRead);*/
+					outPak.send(host, port, sock);
+					/*System.out.println("current op code  " + outPak.get(0)); */
+					
+					//wait for the correct ack. if incorrect, retry up to 5 times
+					while (timeoutLimit!=0) { 
+						try {
+							TFTPpacket ack = TFTPpacket.receive(sock);
+							if (!(ack instanceof TFTPack)){throw new Exception("Client failed");}
+							TFTPack a = (TFTPack) ack;
+							
+							if(a.blockNumber()!=blkNum){ //check ack
+								throw new SocketTimeoutException("last packet lost, resend packet");}
+							/*System.out.println("confirm blk num " + a.blockNumber()+" from "+a.getPort());*/
+							break;
+						} 
+						catch (SocketTimeoutException t) {//resend last packet
+							System.out.println("Resent blk " + blkNum);
+							timeoutLimit--;
+							outPak.send(host, port, sock);
+						}
+					} // end of while
+					if(timeoutLimit==0){throw new Exception("connection failed");}
+				}
+				System.out.println("Transfer completed.(Client " +host +")" );
+				System.out.println("Filename: "+fileName + "\nSHA1 checksum: "+CheckSum.getChecksum(fileName)+"\n");
+			} catch (Exception e) {
+				TFTPerror ePak = new TFTPerror(1, e.getMessage());
+
+				try {
+					ePak.send(host, port, sock);
+				} catch (Exception f) {
+				}
+
+				System.out.println("Client failed:  " + e.getMessage());
+			}
+		}
+	}
+}

src/main/java/ru/redguy/tftpserver/TFTPserverWRQ.java

@@ -0,0 +1,106 @@
+package ru.redguy.tftpserver;
+
+import java.net.*;
+import java.io.*;
+
+
+class TFTPserverWRQ extends Thread {
+
+	protected DatagramSocket sock;
+	protected InetAddress host;
+	protected int port;
+	protected FileOutputStream outFile;
+	protected TFTPpacket req;
+	protected int timeoutLimit = 5;
+	//protected int testloss=0;
+	protected File saveFile;
+	protected String fileName;
+
+	// Initialize read request
+	public TFTPserverWRQ(TFTPwrite request, ErrorEvent event) throws TftpException {
+		try {
+			req = request;
+			sock = new DatagramSocket(); // new port for transfer
+			sock.setSoTimeout(1000);
+
+			host = request.getAddress();
+			port = request.getPort();
+			fileName = request.fileName();
+			//create file object in parent folder
+			saveFile = new File(fileName);
+
+			if (!saveFile.exists()) {
+				outFile = new FileOutputStream(saveFile);
+				TFTPack a = new TFTPack(0);
+				a.send(host, port, sock); // send ack 0 at first, ready to
+											// receive
+				this.start();
+			} else
+				throw new TftpException("access violation, file exists");
+
+		} catch (Exception e) {
+			TFTPerror ePak = new TFTPerror(1, e.getMessage()); // error code 1
+			try {
+				ePak.send(host, port, sock);
+			} catch (Exception f) {
+			}
+
+			event.onClientWriteException(e,request);
+		}
+	}
+
+	public void run() {
+		/*int bytesRead = TFTPpacket.maxTftpPakLen;*/
+		// handle write request
+		if (req instanceof TFTPwrite) {
+			try {
+				for (int blkNum = 1, bytesOut = 512; bytesOut == 512; blkNum++) {
+					while (timeoutLimit != 0) {
+						try {
+							TFTPpacket inPak = TFTPpacket.receive(sock); 
+							//check packet type
+							if (inPak instanceof TFTPerror) {
+								TFTPerror p = (TFTPerror) inPak;
+								throw new TftpException(p.message());
+							} else if (inPak instanceof TFTPdata) {
+								TFTPdata p = (TFTPdata) inPak;
+								/*System.out.println("incoming data " + p.blockNumber());*/
+								// check blk num
+								if (/*testloss==20||*/p.blockNumber() != blkNum) { //expect to be the same
+									//System.out.println("loss. testloss="+testloss+"timeoutLimit="+timeoutLimit);
+									//testloss++;
+									throw new SocketTimeoutException();
+								}
+								//write to the file and send ack
+								bytesOut = p.write(outFile);
+								TFTPack a = new TFTPack(blkNum);
+								a.send(host, port, sock);
+								//testloss++;
+								break;
+							}
+						} catch (SocketTimeoutException t2) {
+							System.out.println("Time out, resend ack");
+							TFTPack a = new TFTPack(blkNum - 1);
+							a.send(host, port, sock);
+							timeoutLimit--;
+						}
+					}
+					if(timeoutLimit==0){throw new Exception("Connection failed");}
+				}
+				outFile.close();
+				System.out.println("Transfer completed.(Client " +host +")" );
+				System.out.println("Filename: "+fileName + "\nSHA1 checksum: "+CheckSum.getChecksum(fileName)+"\n");
+				
+			} catch (Exception e) {
+				TFTPerror ePak = new TFTPerror(1, e.getMessage());
+				try {
+					ePak.send(host, port, sock);
+				} catch (Exception f) {
+				}
+
+				System.out.println("Client failed:  " + e.getMessage());
+				saveFile.delete();
+			}
+		}
+	}
+}

src/main/java/ru/redguy/tftpserver/TFTPwrite.java

@@ -0,0 +1,33 @@
+package ru.redguy.tftpserver;
+
+/////////////////////////////////////////////////////////
+//WRITE packet: put the right opcode and filename, mode//
+//in the 'message'                                     //
+/////////////////////////////////////////////////////////
+public final class TFTPwrite extends TFTPpacket {
+
+//Constructors
+
+    protected TFTPwrite() {
+    }
+
+    public TFTPwrite(String filename, String dataMode) {
+        length = 2 + filename.length() + 1 + dataMode.length() + 1;
+        message = new byte[length];
+
+        put(opOffset, tftpWRQ);
+        put(fileOffset, filename, (byte) 0);
+        put(fileOffset + filename.length() + 1, dataMode, (byte) 0);
+    }
+
+//Accessors
+
+    public String fileName() {
+        return this.get(fileOffset, (byte) 0);
+    }
+
+    public String requestType() {
+        String fname = fileName();
+        return this.get(fileOffset + fname.length() + 1, (byte) 0);
+    }
+}

src/test/java/Main.java

@@ -0,0 +1,47 @@
+import ru.redguy.tftpserver.ErrorEvent;
+import ru.redguy.tftpserver.TFTPServer;
+import ru.redguy.tftpserver.TFTPread;
+import ru.redguy.tftpserver.TFTPwrite;
+
+import java.net.SocketException;
+
+public class Main {
+    public static void main(String[] args) {
+        TFTPServer tftpServer = new TFTPServer();
+        try {
+            tftpServer.start(1000);
+        } catch (SocketException e) {
+            e.printStackTrace();
+        }
+        System.out.println(tftpServer.getPort());
+        tftpServer.onError(new ErrorEvent() {
+            @Override
+            public void onPacketReceiveException(Exception exception) {
+                exception.printStackTrace();
+            }
+
+            @Override
+            public void onPacketReadException(Exception exception) {
+                exception.printStackTrace();
+            }
+
+            @Override
+            public void onPacketWriteException(Exception exception) {
+                exception.printStackTrace();
+            }
+
+            @Override
+            public void onClientReadException(Exception exception, TFTPread tftPread) {
+                exception.printStackTrace();
+                System.out.println(tftPread.fileName());
+            }
+
+            @Override
+            public void onClientWriteException(Exception exception, TFTPwrite tftPwrite) {
+                exception.printStackTrace();
+                System.out.println(tftPwrite.fileName());
+            }
+        });
+        while (true) {}
+    }
+}