Efficient BFS Algorithm in Java .

// Java program to print BFS traversal from a given source vertex.

// BFS(int s) traverses vertices reachable from s.
import java.io.*;
import java.util.*;
 
// This class represents a directed graph using adjacency list
// representation
class Graph
{
    private int V;   // No. of vertices
    private LinkedList adj[]; //Adjacency Lists
 
    // Constructor
    Graph(int v)
    {
        V = v;
        adj = new LinkedList[v];
        for (int i=0; i queue = new LinkedList();
 
        // Mark the current node as visited and enqueue it
        visited[s]=true;
        queue.add(s);
 
        while (queue.size() != 0)
        {
            // Dequeue a vertex from queue and print it
            s = queue.poll();
            System.out.print(s+" ");
 
            // Get all adjacent vertices of the dequeued vertex s
            // If a adjacent has not been visited, then mark it
            // visited and enqueue it
            Iterator i = adj[s].listIterator();
            while (i.hasNext())
            {
                int n = i.next();
                if (!visited[n])
                {
                    visited[n] = true;
                    queue.add(n);
                }
            }
        }
    }
 
    // Driver method to
    public static void main(String args[])
    {
        Graph g = new Graph(4);
 
        g.addEdge(0, 1);
        g.addEdge(0, 2);
        g.addEdge(1, 2);
        g.addEdge(2, 0);
        g.addEdge(2, 3);
        g.addEdge(3, 3);
 
        System.out.println("Following is Breadth First Traversal "+
                           "(starting from vertex 2)");
 
        g.BFS(2);
    }
}

FTP Client and Server in java

 

 

//FTPServer.java

 

import java.net.*;
import java.io.*;
import java.util.*;

public class FTPServer
{
    public static void main(String args[]) throws Exception
    {
        ServerSocket soc=new ServerSocket(5217);
        //System.out.println("FTP Server Started on Port Number 5217");
        while(true)
        {
            System.out.println("Waiting for Connection ...");
            transferfile t=new transferfile(soc.accept());
           
        }
    }
}

class transferfile extends Thread
{
    Socket ClientSoc;

    DataInputStream din;
    DataOutputStream dout;
   
    transferfile(Socket soc)
    {
        try
        {
            ClientSoc=soc;                       
            din=new DataInputStream(ClientSoc.getInputStream());
            dout=new DataOutputStream(ClientSoc.getOutputStream());
            System.out.println("FTP Client Connected ...");
            start();
           
        }
        catch(Exception ex)
        {
        }       
    }
    public void listFiles(){
try{
File directory = new File(".");
 
//get all the files from a directory
File[] fList = directory.listFiles();
 
for (File file : fList){
if (file.isFile()){
dout.writeUTF(file.getName());
}

}
}
catch(Exception e){}
}

    void SendFile() throws Exception
    {    this.listFiles();
           dout.writeUTF("exit");
        String filename=din.readUTF();
        File f=new File(filename);
        if(!f.exists())
        {
            dout.writeUTF("File Not Found");
            return;
        }
        else
        {
            dout.writeUTF("READY");
            FileInputStream fin=new FileInputStream(f);
            int ch;
            do
            {
                ch=fin.read();
                dout.writeUTF(String.valueOf(ch));
            }
            while(ch!=-1);   
            fin.close();   
            dout.writeUTF("File Receive Successfully");                           
        }
    }
   
    void ReceiveFile() throws Exception
    {
        String filename=din.readUTF();
        if(filename.compareTo("File not found")==0)
        {
            return;
        }
        File f=new File(filename);
        String option;
       
        if(f.exists())
        {
            dout.writeUTF("File Already Exists");
            option=din.readUTF();
        }
        else
        {
            dout.writeUTF("SendFile");
            option="Y";
        }
           
            if(option.compareTo("Y")==0)
            {
                FileOutputStream fout=new FileOutputStream(f);
                int ch;
                String temp;
                do
                {
                    temp=din.readUTF();
                    ch=Integer.parseInt(temp);
                    if(ch!=-1)
                    {
                        fout.write(ch);                   
                    }
                }while(ch!=-1);
                fout.close();
                dout.writeUTF("File Send Successfully");
            }
            else
            {
                return;
            }
           
    }

    public void run()
    {
        while(true)
        {
            try
            {
            //System.out.println("Waiting for Command ...");
            String Command=din.readUTF();
            if(Command.compareTo("GET")==0)
            {
                //System.out.println("\tGET Command Received ...");
                SendFile();
                continue;
            }
            else if(Command.compareTo("SEND")==0)
            {
                //System.out.println("\tSEND Command Receiced ...");               
                ReceiveFile();
                continue;
            }
            else if(Command.compareTo("DISCONNECT")==0)
            {
                System.out.println("\tDisconnect Command Received ...");
                System.exit(1);
            }
            }
            catch(Exception ex)
            {
            }
        }
    }
}

 

 

//FTPClient.java

 

import java.net.*;
import java.io.*;
import java.util.*;

class FTPClient
{
    public static void main(String args[]) throws Exception
    {
        Socket soc=new Socket("localhost",5217);
        transferfileClient t=new transferfileClient(soc);
        t.displayMenu();
       
    }
}
class transferfileClient
{
    Socket ClientSoc;

    DataInputStream din;
    DataOutputStream dout;
    BufferedReader br;
    transferfileClient(Socket soc)
    {
        try
        {
            ClientSoc=soc;
            din=new DataInputStream(ClientSoc.getInputStream());
            dout=new DataOutputStream(ClientSoc.getOutputStream());
            br=new BufferedReader(new InputStreamReader(System.in));
        }
        catch(Exception ex)
        {
        }       
    }
    void SendFile() throws Exception
    {       
       
        String filename;
        System.out.print("Enter File Name :");
        filename=br.readLine();
           
        File f=new File(filename);
        if(!f.exists())
        {
            System.out.println("File not Exists...");
            dout.writeUTF("File not found");
            return;
        }
       
        dout.writeUTF(filename);
       
        String msgFromServer=din.readUTF();
        if(msgFromServer.compareTo("File Already Exists")==0)
        {
            String Option;
            System.out.println("File Already Exists. Want to OverWrite (Y/N) ?");
            Option=br.readLine();           
            if(Option=="Y")   
            {
                dout.writeUTF("Y");
            }
            else
            {
                dout.writeUTF("N");
                return;
            }
        }
       
        System.out.println("Sending File ...");
        FileInputStream fin=new FileInputStream(f);
        int ch;
        do
        {
            ch=fin.read();
            dout.writeUTF(String.valueOf(ch));
        }
        while(ch!=-1);
        fin.close();
        System.out.println(din.readUTF());
       
    }
   
    void ReceiveFile() throws Exception
    {    while(true)
    {
    String ms=din.readUTF();
    if(ms.equals("exit"))
    break;
    System.out.println(ms);}
        String fileName;
        System.out.print("Enter File Name :");
        fileName=br.readLine();
        dout.writeUTF(fileName);
        String msgFromServer=din.readUTF();
       
        if(msgFromServer.compareTo("File Not Found")==0)
        {
            System.out.println("File not found on Server ...");
            return;
        }
        else if(msgFromServer.compareTo("READY")==0)
        {
            System.out.println("Receiving File ...");
            File f=new File(fileName);
            if(f.exists())
            {
                String Option;
                System.out.println("File Already Exists. Want to OverWrite (Y/N) ?");
                Option=br.readLine();           
                if(Option=="N")   
                {
                    dout.flush();
                    return;   
                }               
            }
            FileOutputStream fout=new FileOutputStream(f);
            int ch;
            String temp;
            do
            {
                temp=din.readUTF();
                ch=Integer.parseInt(temp);
                if(ch!=-1)
                {
                    fout.write(ch);                   
                }
            }while(ch!=-1);
            fout.close();
            System.out.println(din.readUTF());
               
        }
       
       
    }

    public void displayMenu() throws Exception
    {
        while(true)
        {   
            System.out.println("[ MENU ]");
            System.out.println("1. Send File");
            System.out.println("2. Receive File");
            System.out.println("3. Exit");
            System.out.print("\nEnter Choice :");
            int choice;
            choice=Integer.parseInt(br.readLine());
            if(choice==1)
            {
                dout.writeUTF("SEND");
                SendFile();
            }
            else if(choice==2)
            {
                dout.writeUTF("GET");
                ReceiveFile();
            }
            else
            {
                dout.writeUTF("DISCONNECT");
                System.exit(1);
            }
        }
    }
}

Port Scanner In Java

 

//FileName: PortScanner.java

//Provide the search range while executing the program !

//for example c:/>java PortScanner 5 100

import java.net.*;

public class PortScanner

{

        public static void main(String args[])
       {
       int startPortRange=0;
        int stopPortRange=0;

        startPortRange = Integer.parseInt(args[0]);
        stopPortRange = Integer.parseInt(args[1]);

 

        for(int i=startPortRange; i <=stopPortRange; i++)
       {
                        try
                       {
                        Socket ServerSok = new Socket("127.0.0.1",i);

                 System.out.println("Port which is in use: " + i );

                        ServerSok.close();
                       }
                catch (Exception e)
                       {
                                //System.out.println("Port which is not in use: " + i );
                       }
       
       }
       }
}

Simple program to chat with two computers !

Server.java :


import java.net.*;
import java.io.*;
import java.util.*;
class hh extends Thread
{
 Socket s;
 hh(Socket ss)
 {
 s=ss;
 }
 public void run()
 {
 try
 {
 DataInputStream din= new DataInputStream(s.getInputStream());
 String msg;

 msg=din.readUTF();
 System.out.println(msg);
 }
 catch(Exception e)
 {
 }

 }

}


class server
{
     public static void main(String args[])
   
          {try
  {
          ServerSocket s1=new ServerSocket(1800);
          Socket s=s1.accept();
                   DataOutputStream dos=new DataOutputStream(s.getOutputStream());
                   BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        // dos.writeUTF("Hello this is server!!");
        String msg;
          hh obj=new hh(s);
          Thread th =new Thread(obj);
          th.start();
          System.out.println("Enter your name");
          String name=br.readLine();
while(true)
{
msg=br.readLine();
dos.writeUTF(name+" : "+ msg);
}
  }
catch(Exception e)
{
   System.out.println("OOPS !!");
}
}
}



Here is the client side code !


client.java

import java.net.*;
import java.io.*;
import java.util.*;
class hh extends Thread
{
 Socket s;
 hh(Socket ss)
 {
 s=ss;
 }
 public void run()
 {
   try
 {
 DataInputStream din= new DataInputStream(s.getInputStream());
 String msg;
 while(true)
 {
 msg=din.readUTF();
 System.out.println(msg);
 }
 }
 catch(Exception e)
 {
 }

 }

}
class client
{

     public static void main(String args[])
   
          {
         
       

         
         
          try
  {
          Socket s1=new Socket("localhost",1800);
          BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
          DataOutputStream dos=new DataOutputStream(s1.getOutputStream());
         // dos.writeUTF("Hi this is client!!");
         
          String msg;
          hh obj=new hh(s1);
          Thread th =new Thread(obj);
          obj.start();
          System.out.println("Enter your name");
          String name=br.readLine();
while(true)
{
msg=br.readLine();
dos.writeUTF(name+" : "+msg);
}
        
         }

catch(Exception e)
{
   System.out.println("OOPS Client is OFF !!");
}
}
}