Write a program to implement a distributed chat server using
TCP sockets in ‘C’.

How are PHP arrays different than arrays in other programming languages? Please discuss in depth.

Could i please have some assistance with the following questions.

a) When using the exponential weighted moving average (EWMA) to calculate the running time of the RTT, what does the constant ‘x’ control?

b) Consider a TCP segment. What is sequence number? What is the range of the sequence number? What is the acknowledge number (ACK)?

topic : Introduction to TCP/IP
1) The explanation of how data flows through the network?
2) Understanding of TCP/IP architecture and layers and comparison with the OSI layers?
3) Understanding of the role of protocol analysis in network management?
topic : Name Resolution on IP Network
4) Fundamentals of name resolution protocols ?
5) How name resolution works in IPv4 networks, including the DNS database structure, the DNS namespace, DNS database records, the delegation of DNS authority, and the different types of DNS servers, and explain how name servers work?
6) How name resolution works on IPv6 networks, including the use of AAAA records,the use of source &destination address selection, how rules are organized by the source and destination address algorithms, & end-to-end address selection process?
topic : Transport Layer Protocols
7) Understanding of the differences between connectionless and connection-oriented transport mechanisms?
8) Explain understanding of key features and functions of the User Datagram Protocol (UDP) and the Transmission Control Protocol (TCP) ?

Could i please have some assistance with the following questions.

a) What is the purpose of port numbers? how are they used?

b) Why does TCP probe the network continuously until it experiences a loss?

c) What is the difference between the congestion window and the received window?

d) What is the benefit of TCP Reno over TCP Tahoe?

Create a Python file named num_sum.py that contains:

• The definition of two functions:
  • volume - accepts three parameters and returns the product of them, but displays nothing
  • sum_of_nums - accepts 1 or more numbers and returns their sum, but displays nothing
• A print function call that includes a call to volume, passing 2, 3, and 4
• A print function call that includes a call to sum_of_nums, passing 1, 2, 3, 4, and 5

Creat a python method for a binary tree class that has an inputted lookup value and will output if the lookup values exist within the Binary Tree by returning True or False. Exists within the binary tree -True. No exist within the binary tree - false.Test the method in your code

By using the string function find to find the index of a space; the function length to find the length of the string; and the function substr from a file form firstname, middlename, and lastname to lastname, middlename, and first name. Please help me this is c++ thank you

Could i please have some assistance with the following questions.
a) What are key features of UDP Services?

b) What are some of the advantages of UDP compared to TCP?

c) What is the aim of the connection setup Phase, ie, 3 way handshake, of TCP?

d) What causes duplicate ACK's

In worm, what will happen if the ssh.connect(...) line fails? What code should be added in order to properly handle such scenarios?

Modulation and Encoding

1. Telephone channels have a bandwidth of about 3.1 kHz. Answer the following questions. (If you like, you can use Excel to do the calculations and then cut/paste your analysis into your homework).

a) If a telephone channel’s signal-to-noise ratio (SNR) is 2,000 (the signal strength is 2,000 times as much as the noise strength), use the Shannon Equation to calculate the maximum data rate of a telephone channel?

b) How fast could a telephone channel carry data if the SNR were increased massively, from 2,000 to 20,000? (Note: This would not be realistic in practice.)

c) With an SNR of 2,000, how fast could a telephone channel carry data if the bandwidth were increased to 4 kHz? Show your work or no credit.

d) What do you think is a better way to increase data rate, and why?

Matrix multiplication with arrays

In this question you will verify that the numpy.ndarray matrix multiplication operator, @, does a proper matrix multiplcation. To do this, first write a function, mat_mult(a1, a2) that creates a new 2d array of zeros, and using nested for loops, fill in the elements of the matrix multiplication, and return this new array.

Then, write a second function, matrix_diff(b, c) that takes two arrays as arguments then generates and returns the following ratio:

sqrt((∑(??,?−??,?)^2)/(∑(??,?+??,?)^2))

This function gives a measure of how different two arrays are, giving 0 if the arrays are identical.

Your functions can assume that both matrix arguments are two-dimensional, but they should check that the shapes are compatible and return None if they are not.

Write a python function comparing two binary trees and returns whethere they are same. Input two binary tress and output true or false. True= They are the same, False= They are not . Test the function .

Compare and contrast Web applications and native applications.

When should a native application be selected over a Web application and vice versa?

What advantage does one have over the other? • What are the disadvantages or limitations of each?

Provide URL of your sources.

Assign a new alphabet whenever it sees a new number in those expressions ( Use increment operator(++) so, lets say if x = "a", then x++ would be "b" and so on for as many numbers are there in expressions)

Assignment:Consider the input file “p4in.txt”has the following contents (in java language)
(Assuming that all expressions are correct): so using the valueStack ,uses ArrayStack and operatorStack

Specifications:

1) You must implement ArrayStack.java and modify Positfix.java so that valueStack uses ArrayStack and operatorStack uses LinkedStack.

2) Do this program step by step.

3) It may be easier to use String to split the expression to obtain the array of values.

4) Build your symbol table using single-letter variable name that starts from ‘a’.

Here is the inputfile (p4in.txt)
2 + 3
(2+ 3) * 4
2 * 3 / (4 -5)
2 / 3 + (4 -5)
2 / 3 + c -d
2 ^ 3 ^ 4
(2 ^ 3) ^ 4
2 * (3 / 4 + 5)
(2 + 3) / (4 -5)
2 / (3 -4) * 5
2 - (3 / (4 - 5) * 6 + 0) ^ 1
(2 - 3 * 4) / (5 * 6 ^ 0) * 1 + 8

I need to produce the output file named “p4out.txt” similar to the following:

Here is the output sample p4out.txt
Symbol Table
Variable     Value
a              2
b              3
c              4
d              5
e              6
f              0
g              1
h              8

Input                           Infix    Postfix   Result
2 + 3                           a+b       ab+       5
(2+ 3) * 4                      (a+b)*c   ab+c*    20
2 * 3 / (4 -5)                 all value Omitted downhere
2 / 3 + (4 -5)
2 / 3 + c -d
2 ^ 3 ^ 4
(2 ^ 3) ^ 4
2 * (3 / 4 + 5)
(2 + 3) / (4 -5)
2 / (3 -4) * 5
2 - (3 / (4 - 5) * 6 + 0) ^ 1
(2 - 3 * 4) / (5 * 6 ^ 0) * 1 + 8

Required programs:

ArrayStack.java:

import java.util.Arrays;
import java.util.EmptyStackException;
/**
    A class of stacks whose entries are stored in an array.
    @author Frank M. Carrano
    @author Timothy M. Henry
    @version 4.0
*/
public final class ArrayStack<T> implements StackInterface<T>
{
        private T[] stack;    // Array of stack entries
        private int topIndex; // Index of top entry
   private boolean initialized = false;
        private static final int DEFAULT_CAPACITY = 50;
        private static final int MAX_CAPACITY = 10000;
        
        public ArrayStack()
        {
      this(DEFAULT_CAPACITY);
        } // end default constructor
        
        public ArrayStack(int initialCapacity)
        {
      checkCapacity(initialCapacity);
      
      // The cast is safe because the new array contains null entries
      @SuppressWarnings("unchecked")
      T[] tempStack = (T[])new Object[initialCapacity];
      stack = tempStack;
                topIndex = -1;
      initialized = true;
        } // end constructor

        public void push(T newEntry)
        {
                checkInitialization();
                ensureCapacity();
                stack[topIndex + 1] = newEntry;
                topIndex++;
        } // end push

        public T peek()
        {
                checkInitialization();
                if (isEmpty())
                        throw new EmptyStackException();
                else
         return stack[topIndex];
        } // end peek

        public T pop()
        {
                checkInitialization();
                if (isEmpty())
                        throw new EmptyStackException();
                else
                {
                        T top = stack[topIndex];
                        stack[topIndex] = null;
                        topIndex--; 
         return top;
                } // end if
   } // end pop

   public boolean isEmpty()
        {
                return topIndex < 0;
        } // end isEmpty
        
        public void clear()
        {
                checkInitialization();
      
      // Remove references to the objects in the stack,
      // but do not deallocate the array
                while (topIndex > -1)
      {
                        stack[topIndex] = null;
         topIndex--;
      } // end while
      //        Assertion: topIndex is -1       
        } // end clear
   
   // Throws an exception if this object is not initialized.
   private void checkInitialization()
   {
      if (!initialized)
         throw new SecurityException ("ArrayStack object is not initialized properly.");
   } // end checkInitialization
   
   // Throws an exception if the client requests a capacity that is too large.
   private void checkCapacity(int capacity)
   {
      if (capacity > MAX_CAPACITY)
         throw new IllegalStateException("Attempt to create a stack " +
                                         "whose capacity exceeds " +
                                         "allowed maximum.");
   } // end checkCapacity
    
   // Doubles the size of the array stack if it is full
   // Precondition: checkInitialization has been called.
        private void ensureCapacity()
        {
           if (topIndex >= stack.length - 1) // If array is full, double its size
      {
         int newLength = 2 * stack.length;
         checkCapacity(newLength);
         stack = Arrays.copyOf(stack, newLength);
      } // end if
        } // end ensureCapacity
} // end ArrayStack

LinkedStack.java:

import java.util.EmptyStackException;
/**
   A class of stacks whose entries are stored in a chain of nodes.
   
   @author Frank M. Carrano
   @author Timothy M. Henry
   @version 4.0
*/
public final class LinkedStack<T> implements StackInterface<T>
{
        private Node topNode; // References the first node in the chain
        
        public LinkedStack()
        {
                topNode = null;
        } // end default constructor
        
        public void push(T newEntry)
        {
      topNode = new Node(newEntry, topNode);
//              Node newNode = new Node(newEntry, topNode);
//              topNode = newNode;
        } // end push

        public T peek()
        {
                if (isEmpty())
                        throw new EmptyStackException();
                else
         return topNode.getData();
        } // end peek

        public T pop()
        {
           T top = peek();  // Might throw EmptyStackException
           assert (topNode != null);
      topNode = topNode.getNextNode(); 

           return top;
        } // end pop

/*
// Question 1, Chapter 6: Does not call peek 
        public T pop()
        {
      if (isEmpty())
         throw new EmptyStackException();
      else
                {
         assert (topNode != null);
                        top = topNode.getData();
                        topNode = topNode.getNextNode();
                } // end if
                
                return top;
        } // end pop
*/              

        public boolean isEmpty()
        {
                return topNode == null;
        } // end isEmpty
        
        public void clear()
        {
                topNode = null;  // Causes deallocation of nodes in the chain
        } // end clear

        private class Node
        {
      private T    data; // Entry in stack
      private Node next; // Link to next node

      private Node(T dataPortion)
      {
         this(dataPortion, null);
      } // end constructor

      private Node(T dataPortion, Node linkPortion)
      {
         data = dataPortion;
         next = linkPortion;    
      } // end constructor

      private T getData()
      {
         return data;
      } // end getData

      private void setData(T newData)
      {
         data = newData;
      } // end setData

      private Node getNextNode()
      {
         return next;
      } // end getNextNode

      private void setNextNode(Node nextNode)
      {
         next = nextNode;
      } // end setNextNode
        } // end Node
} // end LinkedStack

Postfix.java:

/**
   A class that represents a postfix expression.
   Based on pseudocode in Segments 5.16 and 5.18.

   @author Frank M. Carrano
   @author Timothy M. Henry
   @version 4.0
*/
public class Postfix
{
   /** Creates a postfix expression that represents a given infix expression.
       Segment 5.16.
       @param infix  A string that is a valid infix expression.
       @return  A string that is the postfix expression equivalent to infix. */
   public static String convertToPostfix(String infix)
   {
      StackInterface<Character> operatorStack = new LinkedStack<Character>();
      StringBuilder postfix = new StringBuilder();
      int characterCount = infix.length();
      char topOperator;

      for (int index = 0; index < characterCount; index++)
      {
         boolean done = false;
         char nextCharacter = infix.charAt(index);

         if (isVariable(nextCharacter))
            postfix = postfix.append(nextCharacter);
         else
         {
            switch (nextCharacter)
            {
               case '^':
                  operatorStack.push(nextCharacter);
                  break;

               case '+': case '-': case '*': case '/':
                  while (!done && !operatorStack.isEmpty())
                  {
                     topOperator = operatorStack.peek();

                     if (getPrecedence(nextCharacter) <= getPrecedence(topOperator))
                     {
                        postfix = postfix.append(topOperator);
                        operatorStack.pop();
                     }
                     else
                        done = true;
                  } // end while

                  operatorStack.push(nextCharacter);
                  break;

               case '(':
                  operatorStack.push(nextCharacter);
               break;

               case ')': // Stack is not empty if infix expression is valid
                  topOperator = operatorStack.pop();
                  while (topOperator != '(')
                  {
                     postfix = postfix.append(topOperator);
                     topOperator = operatorStack.pop();
                  } // end while
                  break;

               default: break; // Ignore unexpected characters
            } // end switch
         } // end if
      } // end for

      while (!operatorStack.isEmpty())
      {
         topOperator = operatorStack.pop();
         postfix = postfix.append(topOperator);
      } // end while

      return postfix.toString();
   } // end convertToPostfix

   // Indicates the precedence of a given operator.
   // Precondition: operator is a character that is (, ), +, -, *, /, or ^.
   // Returns an integer that indicates the precedence of operator:
   //         0 if ( or ), 1 if + or -, 2 if * or /, 3 if ^,
   //         -1 if anything else. */
   private static int getPrecedence(char operator)
   {
      switch (operator)
      {
         case '(': case ')': return 0;
         case '+': case '-': return 1;
         case '*': case '/': return 2;
         case '^':           return 3;
      } // end switch

      return -1;
   } // end getPrecedence

   private static boolean isVariable(char character)
   {
      return Character.isLetter(character);
   } // end isVariable

   /** Evaluates a postfix expression.
       Segment 5.18
       @param postfix  a string that is a valid postfix expression.
       @return  the value of the postfix expression. */
   public static double evaluatePostfix(String postfix)
   {
      StackInterface<Double> valueStack = new LinkedStack<Double>();
      int characterCount = postfix.length();

      for (int index = 0; index < characterCount; index++)
      {
         char nextCharacter = postfix.charAt(index);

         switch(nextCharacter)
         {
            case 'a': case 'b': case 'c': case 'd': case 'e':
               valueStack.push(valueOf(nextCharacter));
               break;

            case '+': case '-': case '*': case '/': case '^':
               Double operandTwo = valueStack.pop();
               Double operandOne = valueStack.pop();
               Double result = compute(operandOne, operandTwo, nextCharacter);
               valueStack.push(result);
               break;

            default: break; // Ignore unexpected characters
         } // end switch
      } // end for

      return (valueStack.peek()).doubleValue();
   } // end evaluatePostfix

   private static double valueOf(char variable)
   {
      switch (variable)
      {
         case 'a': return 2.5;
         case 'b': return 3.0;
         case 'c': return 4.0;
         case 'd': return 12.0;
         case 'e': return 16.5;
      } // end switch

      return 0; // Unexpected character
   } // end valueOf

   private static Double compute(Double operandOne, Double operandTwo, char operator)
   {
      double result;

      switch (operator)
      {
         case '+':
            result = operandOne.doubleValue() + operandTwo.doubleValue();
            break;

         case '-':
            result = operandOne.doubleValue() - operandTwo.doubleValue();
            break;

         case '*':
            result = operandOne.doubleValue() * operandTwo.doubleValue();
             break;

         case '/':
            result = operandOne.doubleValue() / operandTwo.doubleValue();
            break;

         case '^':
            result = Math.pow(operandOne.doubleValue(), operandTwo.doubleValue());
            break;

         default:    // Unexpected character
            result = 0;
            break;
      } // end switch

      return result;
   } // end compute
} // end Postfix

StackInterface.java:

/**
   An interface for the ADT stack.
   @author Frank M. Carrano
   @author Timothy M. Henry
   @version 4.0
*/
public interface StackInterface<T>
{
   /** Adds a new entry to the top of this stack.
       @param newEntry  An object to be added to the stack. */
   public void push(T newEntry);
  
   /** Removes and returns this stack's top entry.
       @return  The object at the top of the stack. 
       @throws  EmptyStackException if the stack is empty before the operation. */
   public T pop();
  
   /** Retrieves this stack's top entry.
       @return  The object at the top of the stack.
       @throws  EmptyStackException if the stack is empty. */
   public T peek();
  
   /** Detects whether this stack is empty.
       @return  True if the stack is empty. */
   public boolean isEmpty();
  
   /** Removes all entries from this stack. */
   public void clear();
} // end StackInterface

Driver.java:

/**
   A driver that demonstrates the class Postfix.
   
   @author Frank M. Carrano
   @author Timothy M. Henry
   @version 4.1
*/
public class Driver
{
        public static void main(String[] args) 
        {
                System.out.println("Testing postfix expressions with\n" +
                                   "a = 2, b = 3, c = 4, d = 5, e = 6\n\n");

                testPostfix("a+b");
                testPostfix("(a + b) * c");
                testPostfix("a * b / (c - d)");
                testPostfix("a / b + (c - d)");
                testPostfix("a / b + c - d");
                testPostfix("a^b^c");
                testPostfix("(a^b)^c");
                testPostfix("a*(b/c+d)");

                System.out.println("Testing Question 6, Chapter 5:\n");
                testPostfix("(a+b)/(c-d)");         // Question 6a, Chapter 5
                testPostfix("a/(b-c)*d");           // Question 6b
                testPostfix("a-(b/(c-d)*e+f)^g");   // Question 6c
                testPostfix("(a-b*c)/(d*e^f*g+h)"); // Question 6d

                System.out.println("Testing Question 7, Chapter 5:\n");
                System.out.println("Q7a: ae+bd-/ : "   + Postfix.evaluatePostfix("ae+bd-/") + "\n");
                System.out.println("Q7b: abc*d*- : "   + Postfix.evaluatePostfix("abc*d*-") + "\n");
                System.out.println("Q7c: abc-/d* : "   + Postfix.evaluatePostfix("abc-/d*") + "\n");
                System.out.println("Q7d: ebca^*+d- : " + Postfix.evaluatePostfix("ebca^*+d-") + "\n");
                System.out.println("\n\nDone.");
        }  // end main
        
        public static void testPostfix(String infixExpression)
        {
                System.out.println("Infix:   " + infixExpression);
                String postfixExpression =  Postfix.convertToPostfix(infixExpression);
                System.out.println("Postfix: " + postfixExpression);
                System.out.println("\n");
        } // end testPostfix 
}  // end Driver

/*
 Testing postfix expressions with
 a = 2, b = 3, c = 4, d = 5, e = 6
 
 
 Infix:   a+b
 Postfix: ab+
 
 
 Infix:   (a + b) * c
 Postfix: ab+c*
 
 
 Infix:   a * b / (c - d)
 Postfix: ab*cd-/
 
 
 Infix:   a / b + (c - d)
 Postfix: ab/cd-+
 
 
 Infix:   a / b + c - d
 Postfix: ab/c+d-
 
 
 Infix:   a^b^c
 Postfix: abc^^
 
 
 Infix:   (a^b)^c
 Postfix: ab^c^
 
 
 Infix:   a*(b/c+d)
 Postfix: abc/d+*
 
 
 Testing Question 6, Chapter 5:
 
 Infix:   (a+b)/(c-d)
 Postfix: ab+cd-/
 
 
 Infix:   a/(b-c)*d
 Postfix: abc-/d*
 
 
 Infix:   a-(b/(c-d)*e+f)^g
 Postfix: abcd-/e*f+g^-
 
 
 Infix:   (a-b*c)/(d*e^f*g+h)
 Postfix: abc*-def^*g*h+/
 
 
 Testing Question 7, Chapter 5:
 
 Q7a: ae+bd-/ : -4.0
 
 Q7b: abc*d*- : -58.0
 
 Q7c: abc-/d* : -10.0
 
 Q7d: ebca^*+d- : 49.0
 
 
 
 Done.
 */