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server.cpp
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server.cpp
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/*****************************************************************************************************************************************
* *
* @author: Ankit Dimri *
* Multithreaded udp server to reverse a given input string by the client. *
* *
*****************************************************************************************************************************************/
#include <iostream>
#include <sys/socket.h>
#include <netdb.h>
#include <unistd.h>
#include <cstring>
#include <stdio.h>
#include <algorithm>
#include <pthread.h>
#include <signal.h>
#include <arpa/inet.h>
pthread_t threads [100]; // at max 100 threads
int threadno = 0, fd;
/* Signal handler to handle ctrl+c to close server socket before terminating the server */
void sig_handler(int signo) {
if (signo == SIGINT) {
std::cout << "\t Exiting..." << '\n';
close (fd);
exit (1);
}
}
/* Structure to hold the necessary parameters to pass into the threaded reverse_string function */
struct req {
int reqno;
int des;
char str [2048];
socklen_t addlen;
sockaddr_in clientaddr;
};
/*
* Function called in threads to reverse the string and send the packet back to the respective
* client socket with the string sent reversed
*/
void* reverse_string (void*);
int main(int argc, char const *argv[]) {
/* server name : Misty */
sockaddr_in mistaddr; // server address
sockaddr_in clientaddr; // client address
socklen_t addrlen = sizeof(clientaddr);
int recvlen, msgcnt = 0;
char buf [2048]; // Hold buffer sent in udp packet
/* Create socket */
if ((fd = socket (AF_INET, SOCK_DGRAM, 0)) == -1) {
std::cout << "\n\t Socket creation failed...\n\t Exiting..." << '\n';
return 0;
}
std::cout << "\n\t Socket created..." << '\n';
/* clear the memory allocated */
memset ((sockaddr*)&mistaddr, 0, sizeof (mistaddr));
mistaddr.sin_family = AF_INET; // IPv4 address family
mistaddr.sin_addr.s_addr = htonl (INADDR_ANY); // Give the local machine address
mistaddr.sin_port = htons (1721); // Port at which server listens to the requests
/* Bind the IP address and the port number to create the socket */
if (bind (fd, (sockaddr*)&mistaddr, sizeof (mistaddr)) == -1) {
std::cout << "\n\t Binding failed...\n\t Exiting..." << '\n';
return 0;
}
std::cout << "\n\t Binding succesful" << '\n';
/* Signal catching */
signal(SIGINT, sig_handler);
signal(SIGTSTP, sig_handler);
/* Infinte server loop */
while (1) {
/* Server listing */
std::cout << "\n\t Waiting on port " << ntohs(mistaddr.sin_port) << '\n';
/* waiting to recieve the requests from client at port */
/* Code blocking function */
recvlen = recvfrom (fd, buf, 2048, 0, (sockaddr*) &clientaddr, &addrlen);
/* Counting number of messages recieved */
msgcnt++;
/* Filling the parameter values of the threaded function */
req *r = new req; // allocate memory
bzero (r, sizeof (req)); // Clear memory
r->reqno = msgcnt;
r->addlen = addrlen;
r->clientaddr = clientaddr;
r->des = fd;
strcpy (r->str, buf);
/* Create thread to execute the client requests paralelly */
pthread_create (&threads [threadno++], NULL, reverse_string, (void*)r);
if (threadno == 100)
threadno = 0;
memset (buf, 0, sizeof (buf)); // clear buffer
}
}
// Function to reverse the string and send back the packet */
void* reverse_string (void* r) {
req rq = *((req*)r); // Type casting
std::cout << "\n String: " << rq.str << " | From: " << inet_ntoa (rq.clientaddr.sin_addr) << ":" << ntohs (rq.clientaddr.sin_port);
std::cout << " (message count: " << rq.reqno << ")" << '\n';
std::reverse( rq.str, &rq.str[ strlen( rq.str ) ] ); // reversing the string
/* Send the reversed string back to the client at its socket */
sendto (rq.des, rq.str, strlen (rq.str), 0, (sockaddr*) &rq.clientaddr, rq.addlen);
return NULL;
}