// Client side implementation of UDP client-server model
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>

#define PORT 8008
#define MAXLINE 1024

// Driver code
int main() {
        char buffer[MAXLINE];
        struct sockaddr_in servaddr;

        // Creating socket file descriptor

        int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
        if ( sockfd < 0 ) {
                perror("socket creation failed");
                exit(EXIT_FAILURE);
        }

        struct timeval timeout;
        timeout.tv_sec = 1; //Wait 1 second
        timeout.tv_usec = 0;

        if (setsockopt (sockfd, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof timeout) < 0) perror("setsockopt failed\n");

        if (setsockopt (sockfd, SOL_SOCKET, SO_SNDTIMEO, &timeout, sizeof timeout) < 0) perror("setsockopt failed\n");

        memset(&servaddr, 0, sizeof(servaddr));

        // Filling server information
        servaddr.sin_family = AF_INET;
        servaddr.sin_port = htons(PORT);
        servaddr.sin_addr.s_addr = inet_addr("192.168.4.65");

        for(int i = 0; i < 10; ++i){
                char* message = "PING";
                int sendStatus = sendto(sockfd, (const char *)message, strlen(message), MSG_CONFIRM, (const struct sockaddr *) &servaddr, sizeof(servaddr));
                if(sendStatus >= 0){
                        printf("Sent PING\n");
                }else{
                        printf("Send failed\n");
                        continue;
                }

                int len = sizeof(struct sockaddr_in);
                int bytesRecieved = recvfrom(sockfd, (char *)buffer, MAXLINE, MSG_WAITALL, (struct sockaddr *) &servaddr, &len); //We can reuse servaddr because the port the server sends messages from is the same one we send to
                if(bytesRecieved >= 0){
                        buffer[bytesRecieved] = '\0';
                        printf("Recieved %s\n", buffer);
                }else{
                        printf("Recieved nothing: Packet Dropped\n", buffer);
                }
        }

        close(sockfd);

        return 0;
}

#include <stdio.h>
#include <string.h>
#include <unistd.h>

#define READ 0 /* The index of the read end of the pipe */
#define WRITE 1 /* The index of the write end of the pipe */
char * phrase = "This goes in the pipe";
int main() {
  int fd[2], bytesRead;
  char message[100]; /* Parent process' message buffer */
  pipe(fd); /* Create unnamed pipe */
  if (fork() == 0) /* Child, writer */ {
    close(fd[READ]); /* Close unused end */
    write(fd[WRITE], phrase, strlen(phrase) + 1); /* Include NULL */
    close(fd[WRITE]); /* Close used end */
  } else /* Parent, reader */ {
    close(fd[WRITE]); /* Close unused end */
    bytesRead = read(fd[READ], message, 100);
    printf("Parent just read %i bytes: %s\n", bytesRead, message);
    close(fd[READ]); /* Close used end */
  }
}

// compile: gcc socketTCPServer.c -o socketTCPServer.out
// usage  : ./socketTCPServer.out port
// Server

#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>

int main(int argc, char *argv[]){
        int listenfd = 0, connfd = 0, cli_size, portno;

        struct sockaddr_in serv_addr, cli_addr;

        char sendBuff[1025];

        if((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1){
                printf("socket error\n");
                exit(EXIT_FAILURE);
        }

        memset(&serv_addr, '0', sizeof(serv_addr));
        memset(sendBuff, '0', sizeof(sendBuff));

        serv_addr.sin_family = AF_INET;
        serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
        portno = atoi(argv[1]);
        serv_addr.sin_port = htons(portno);

        const int on = 1;
        setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));

        if(bind(listenfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) == -1){
                printf("bind error\n");
                exit(EXIT_FAILURE);
        }


        if(listen(listenfd, 5) == -1){
                printf("listen error\n");
                exit(EXIT_FAILURE);
        }

        while(1){
                cli_size = sizeof(cli_addr);
                if((connfd = accept(listenfd, (struct sockaddr*)&cli_addr, &cli_size)) == -1){
                        printf("accept error\n");
                        exit(EXIT_FAILURE);
                }

                strcpy(sendBuff, "Server Message: SUCCESS\n");
                write(connfd, sendBuff, strlen(sendBuff));

                close(connfd);
                sleep(1);
        }
        return 0;
}

// The following code is the fast inverse square root implementation from Quake III Arena
// this code has been stripped of C preprocessor directives, but includes the exact original comment text
float Q_rsqrt( float number )
{
	long i;
	float x2, y;
	const float threehalfs = 1.5F;

	x2 = number * 0.5F;
	y  = number;
	i  = * ( long * ) &y;                       // evil floating point bit level hacking
	i  = 0x5f3759df - ( i >> 1 );               // what the fuck? 
	y  = * ( float * ) &i;
	y  = y * ( threehalfs - ( x2 * y * y ) );   // 1st iteration
//	y  = y * ( threehalfs - ( x2 * y * y ) );   // 2nd iteration, this can be removed

	return y;
}

#include <stdio.h>
#include <stdlib.h>

// give an array of identical coins (ints), represented by 1's and one 2
// we can find the heavy coin (2) by summing the contents of the thirds

int sum_subarr(int arr[], int l, int r){
  int sum = 0;
  for(int i = l; i <= r; i++)
  {
    sum += arr[i];
  }

  return sum;
}

int heavy_coin(int arr[], int l, int r){

  if(r == l)
  {
    return r;
  }
  int midl = l + (r - l)/3;
  int midr = r - (r - l)/3;
  int lw = sum_subarr(arr, l, midl);
  int mw = sum_subarr(arr, midl + 1, midr);

  if ( lw > mw )
  {
    return heavy_coin(arr, l, midl);
  }
  else if ( lw < mw )
  {
    return heavy_coin(arr, midl + 1, midr);
  }
  else
  {
    return heavy_coin(arr, midr + 1, r);
  }

}

int main(int argc, char *argv[])
{

  int arr[] = {1,1,1,1,2,1,1,1,1};
  int l = 0;
  int r = 8;
  int res = -1;

  res = heavy_coin(arr, l, r);

  printf("Hevy coin is at index: %d\n", res);

  return EXIT_SUCCESS;
}

// Server side implementation of UDP client-server model
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>

#define PORT     8008
#define MAXLINE 1024

// Driver code
int main(){
        int sockfd;
        char buffer[MAXLINE];
        char *hello = "Hello from server";
        struct sockaddr_in servaddr, cliaddr;

        // Creating socket file descriptor
        if ( (sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0 ) {
                perror("socket creation failed");
                exit(EXIT_FAILURE);
        }

        memset(&servaddr, 0, sizeof(servaddr));
        memset(&cliaddr, 0, sizeof(cliaddr));

        // Filling server information
        servaddr.sin_family    = AF_INET; // IPv4
        servaddr.sin_addr.s_addr = INADDR_ANY;
        servaddr.sin_port = htons(PORT);

        // Bind the socket with the server address
        if ( bind(sockfd, (const struct sockaddr *)&servaddr, sizeof(servaddr)) < 0 ){
                perror("bind failed");
                exit(EXIT_FAILURE);
        }

        int len, n;

        len = sizeof(cliaddr);  //len is value/result

        n = recvfrom(sockfd, (char *)buffer, MAXLINE, MSG_WAITALL, ( struct sockaddr *) &cliaddr, &len);
        buffer[n] = '\0';
        printf("Client : %s\n", buffer);
        sendto(sockfd, (const char *)hello, strlen(hello), MSG_CONFIRM, (const struct sockaddr *) &cliaddr, len);
        printf("Hello message sent.\n");

        return 0;
}