You must create a communication program in the form of a client and a server.
- The server must be started first. After its launch, it has to print its PID.
- The client takes two parameters: the server PID, the string to send (./client PID_NUMBER "string to send")
- The client must send the string passed as a parameter to the server.
- Once the string has been received, the server must print it.
- The server has to display the string pretty quickly. Quickly means that if you think it takes too long, then it is probably too long. 1 second for displaying 100 characters is way too much!
- Your server should be able to receive strings from several clients in a row without needing to restart.
- The communication between your client and your server has to be done only using UNIX signals. You can only use these two signals: SIGUSR1 and SIGUSR2. Linux system does NOT queue signals when you already have pending signals of this type! Bonus time?
- The server acknowledges every message received by sending back a signal to the client.
- Unicode characters support! UTF-8
The bonus part will only be assessed if the mandatory part is PERFECT. Perfect means the mandatory part has been integrally done and works without malfunctioning. If you have not passed ALL the mandatory requirements, your bonus part will not be evaluated at all.### Project instructions
- Name your executable files client and server
- You have to turn in a Makefile which will compile your source files. It must not relink.
- You can definitely use your libft.
- You have to handle errors thoroughly.
- In no way your program should quit unexpectedly (segmentation fault, bus error, double free, and so forth).
- Your program mustn’t have memory leaks.
- You can have one global variable per program (one for the client and one for the server), but you will have to justify their use.
- In order to complete the mandatory part, you are allowed to use the following functions:
writeft_printfand any equivalent YOU codedsignalsigemptyset & sigaddsetsigactionkillgetpidmallocfreepausesleepusleepexit
Signals are standardized messages sent to a running program to trigger specific behavior, such as quitting or error handling. They are a limited form of inter-process communication (IPC), typically used in POSIX-compliant operating systems.
When a signal is sent. the operating system interrupts the target process normal flow of executing to deliver the signal. Execution can be interrupted during any non-atomic instruction. If the process has previously registered a signal handler, that routine is executed. Otherwise, the default signal handler is executed.
A signal is an event generated by the UNIX and Linux systems in response to some condition. Upon receipt of a signal, a process may take action.
A signal is just like an interrupt; when it is generated at the user level, a call is made to the kernel of the OS, which then acts accordingly. \
There are two types of signals:
- Maskable: signals which can be changed or ignored by the user (e.g., Ctrl+C)
- None-Maskable: Signals which cannot be changed or ignored by the user. These typically occurs when the user is signaled for non-recoverable hardware errors.
Signal handlers can be installed with the system calls :
-- signal(2)
or
-- sigaction(2)
If a signal handler is not installer for a particular signal, the default handler is user. Otherwise the signal is intercepted and the signal handler is invoked.
The signals are defined in the header file signal.h as a macro constant. Signal name has started with a “SIG” and followed by a short description of the signal. So, every signal has a unique numeric value. Your program should always use the name of the signals, not the signals number. The reason is signal number can differ according to system but meaning of names will be standard.
The macro NSIG is the total number of signal defined. The value of NSIG is one greater than the total number of signal defined (All signal numbers are allocated consecutively).
The following is a list of all signals with names as in the include file <signal.h>:
No Name Default Action Description
1 SIGHUP terminate process terminal line hangup
2 SIGINT terminate process interrupt program
3 SIGQUIT create core image quit program
4 SIGILL create core image illegal instruction
5 SIGTRAP create core image trace trap
6 SIGABRT create core image abort program (formerly SIGIOT)
7 SIGEMT create core image emulate instruction executed
8 SIGFPE create core image floating-point exception
9 SIGKILL terminate process kill program
10 SIGBUS create core image bus error
11 SIGSEGV create core image segmentation violation
12 SIGSYS create core image non-existent system call invoked
13 SIGPIPE terminate process write on a pipe with no reader
14 SIGALRM terminate process real-time timer expired
15 SIGTERM terminate process software termination signal
16 SIGURG discard signal urgent condition present on socket
17 SIGSTOP stop process stop (cannot be caught or ignored)
18 SIGTSTP stop process stop signal generated from keyboard
19 SIGCONT discard signal continue after stop
20 SIGCHLD discard signal child status has changed
21 SIGTTIN stop process background read attempted from control terminal
22 SIGTTOU stop process background write attempted to control terminal
23 SIGIO discard signal I/O is possible on a descriptor (see fcntl(2))
24 SIGXCPU terminate process cpu time limit exceeded (see setrlimit(2))
25 SIGXFSZ terminate process file size limit exceeded (see setrlimit(2))
26 SIGVTALRM terminate process virtual time alarm (see setitimer(2))
27 SIGPROF terminate process profiling timer alarm (see setitimer(2))
28 SIGWINCH discard signal Window size change
29 SIGINFO discard signal status request from keyboard
30 SIGUSR1 terminate process User defined signal 1
31 SIGUSR2 terminate process User defined signal 2