Fast inverse square root
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// 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 RECIEVE_BUFFER_SIZE 1024// Driver codeint main() {//Create a UDP socket//int socket(int domain, int type, int protocol);//Domain is the place where the data goes. AF_BLUETOOTH, AF_INET6, AF_UNIX is local communication between different programs//Type is the type of connection, so connection based (TCP), connectionless (UDP) or somewhere in between or beyond//Protocol is an enum or flags that give some more options specific to that type. For SOCK_STREAM, you can force it to use SCTP instead of TCP. For SOCK_RAW, it can give you control over the ip frame, and even the ethernet frame.//So this function makes a file descriptor to an IPV4 UDP 'connection' with no options.int sockfd = socket(AF_INET, SOCK_DGRAM, 0);// Creating socket file descriptorif ( sockfd < 0) {perror("socket creation failed");exit(EXIT_FAILURE);}struct sockaddr_in serverAddress;memset(&serverAddress, 0, sizeof(serverAddress));// Filling server informationserverAddress.sin_family = AF_INET; // IPv4serverAddress.sin_addr.s_addr = INADDR_ANY;serverAddress.sin_port = htons(PORT);// Bind the socket with the server addressif(bind(sockfd, (const struct sockaddr*)&serverAddress, sizeof(serverAddress))){ //Bind returns 0 if succeeded, or -1 if failed. -1 is still true.perror("bind failed");exit(EXIT_FAILURE);}struct sockaddr_in clientAddress; unsigned int clientAddressSize = sizeof(clientAddress);memset(&clientAddress, 0, clientAddressSize);char buffer[RECIEVE_BUFFER_SIZE];while(1){int bytesRecieved = recvfrom(sockfd, (char*)buffer, RECIEVE_BUFFER_SIZE, MSG_WAITALL, (struct sockaddr*) &clientAddress, &clientAddressSize); //sets clientAddress to the client's address and the new sizebuffer[bytesRecieved] = '\0';//printf("Client : %s\n", buffer);//The client might be like PINGUIN or something, but this is to ensure PING\n\r also gets acceptedif(bytesRecieved >= 4 && (strncmp("PING", buffer, 4) == 0)){const char* responseMessage = "PONG";sendto(sockfd, (const char*)responseMessage, strlen(responseMessage), MSG_CONFIRM, (const struct sockaddr*) &clientAddress, clientAddressSize);//printf("Hello message sent.\n");}else{printf("Server bytes recieved: %d\nServer message recieved: %s", bytesRecieved, buffer);}}return 0;}
#include <stdio.h>#include <sys/types.h>#include <unistd.h>int glbvar = 6;int main() {int locvar = 88;pid_t pid;printf("Before fork()\n");if ((pid = fork()) == 0) {/* child */glbvar++;locvar++;} else if (pid > 0) {/* parent */sleep(2);} elseperror("fork error");printf("pid=%d, glbvar=%d, locvar=%d\n", getpid(), glbvar, locvar);return 0;} /* end main */
#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <sys/types.h>#include <sys/wait.h>int main() {char * cmd[] = {"who","ls","date"};int i;while (1) {printf("0=who 1=ls 2=date : ");scanf("%d", & i);if (fork() == 0) {/* child */execlp(cmd[i], cmd[i], (char * ) 0);printf("execlp failed\n");exit(1);} else {/* parent */wait((int * ) 0);printf("child finished\n");}} /* while */} /* main */
// 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;}
// compile: gcc socketTCPClient.c -o socketTCPClient.out// usage : ./socketTCPClient.out port// Doesn't send anything, just connects and prints out the response from the server#include <sys/socket.h>#include <sys/types.h>#include <netinet/in.h>#include <netdb.h>#include <stdio.h>#include <string.h>#include <stdlib.h>#include <unistd.h>#include <errno.h>#include <arpa/inet.h>int main(int argc, char *argv[]){int sockfd = 0, n = 0, portno;char recvBuff[1025];struct sockaddr_in serv_addr;memset(recvBuff, '0', sizeof(recvBuff));if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0){printf("socket error\n");exit(EXIT_FAILURE);}serv_addr.sin_family = AF_INET;portno = atoi(argv[1]);serv_addr.sin_port = htons(portno);serv_addr.sin_addr.s_addr = inet_addr("127.0.0.1");if(connect(sockfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) < 0){printf("connect error\n");exit(EXIT_FAILURE);}while((n = read(sockfd, recvBuff, sizeof(recvBuff)-1)) > 0){recvBuff[n] = 0;if (fputs(recvBuff, stdout) == EOF){printf("fputs error\n");}}if(n < 0){printf("read error\n");}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 */}}