Project n°6 - minitalk

The purpose of this project is to code a small data exchange program using UNIX signals.

Goals

Create a communication program in the form of a client and server. The server must be launched first, and after being launched it must display its PID. The client must communicate the string passed as a parameter to the server. Once the string has been received, the server must display it. Communication between your programs should ONLY be done using UNIX signals.

The client will take as parameters:

• The server PID.
• The string that should be sent.

Only SIGUSR1 and SIGUSR2 can be used.

Functions allowed

• malloc(), free()
• write(), printf()
• signal(), sigfillset(), sigaddset(), sigaction()
• kill(), getpid()
• pause(), sleep(), usleep()
• exit()

UNIX signals

SIGUSR1 & SIGUSR2

These signals are used for various other purposes. In general, they will not affect your program unless it explicitly uses them for something.

The SIGUSR1 and SIGUSR2 signals are set aside for us to use any way we want. They’re useful for simple interprocess communication, if we write a signal handler for them in the program that receives the signal.

There is an example showing the use of SIGUSR1 and SIGUSR2 in Signaling Another Process.

The default action is to terminate the process.

Bitwise operation

This type of operator treats its operands as 32-bit binary data, rather than decimal, hexadecimal, or octal data. These operators process this data according to their binary representation but return standard numeric values in their original format.

Operator	Denomination	Effect	Syntax	Result
&	ET bit-by-bit	Returns 1 if the two bits of the same weight are at 1	9 & 12 (1001 & 1100)	8 (1000)
|	OU bit-by-bit	Returns 1 if either of the two equally significant bits is 1 (or both)	9 | 12 (1001 | 1100)	13 (1101)
^	OU bit-by-bit exclusif	Returns 1 if one of the two bits of equal weight is 1 (but not both)	9 ^ 12 (1001 ^ 1100)	5 (0101)

AND (&)

12 = 00001100 (In Binary)
25 = 00011001 (In Binary)

Bit Operation of 12 and 25
  00001100
& 00011001
  ________
  00001000  = 8 (In decimal)

OR (|)

12 = 00001100 (In Binary)
25 = 00011001 (In Binary)

Bitwise OR Operation of 12 and 25
  00001100
| 00011001
  ________
  00011101  = 29 (In decimal)

XOR

12 = 00001100 (In Binary)
25 = 00011001 (In Binary)

Bitwise XOR Operation of 12 and 25
  00001100
^ 00011001
  ________
  00010101  = 21 (In decimal)

Right Shift Operator

Right shift operator shifts all bits towards right by certain number of specified bits. It is denoted by >>.

212 = 11010100 (In binary)
212>>2 = 00110101 (In binary) [Right shift by two bits]
212>>7 = 00000001 (In binary)
212>>8 = 00000000 
212>>0 = 11010100 (No Shift)

Left Shift Operator

Left shift operator shifts all bits towards left by a certain number of specified bits. The bit positions that have been vacated by the left shift operator are filled with 0. The symbol of the left shift operator is <<.

212 = 11010100 (In binary)
212<<1 = 110101000 (In binary) [Left shift by one bit]
212<<0 = 11010100 (Shift by 0)
212<<4 = 110101000000 (In binary) =3392(In decimal)

Bonus

• The server confirms every signal received by sending a signal to the client. (Not implemented)
• Support Unicode characters!