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socketUDPPingClient.c

Aug 5, 2023LeifMessinger
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fork() example

Nov 19, 2022CodeCatch

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#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
int main() {
pid_t pid; /* could be int */
int i;
pid = fork();
printf("PID=%d\n", pid);
if (pid > 0) {
/* parent */
for (i = 0; i < 10; i++)
printf("\t\t\tPARENT %d\n", i);
} else {
/* child */
for (i = 0; i < 10; i++)
printf("CHILD %d\n", i);
}
return 0;
}

Bitwise operators with pointers

Nov 18, 2022AustinLeath

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#include <stdio.h>
#include <stdlib.h>
int main(){
int * int_ptr;
int_ptr = (int *)malloc(2*sizeof(int));
if(!int_ptr) {
printf("Something went wrong while allocating memory. Exiting...");
exit(1);
}
printf("Enter first integer: ");
scanf("%i", &int_ptr[0]);
printf("Enter second integer: ");
scanf("%i", &int_ptr[1]);
printf("Original values: 1st = %i 2nd = %i\n",int_ptr[0], int_ptr[1]);
int_ptr[0] = int_ptr[0] ^ int_ptr[1];
//printf("%i\n", int_ptr[0]);
int_ptr[1] = int_ptr[0] ^ int_ptr[1];
//printf("%i\n", int_ptr[1]);
int_ptr[0] = int_ptr[0] ^ int_ptr[1];
//printf("%i\n", int_ptr[0]);
printf("Swapped values: 1st = %i 2nd = %i\n", int_ptr[0], int_ptr[1]);
free(int_ptr);
exit(0);
}

socketUDPServer.c

Aug 5, 2023LeifMessinger

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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
const char* responseMessage = "Hello from server";
// Driver code
int 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 descriptor
if ( sockfd < 0) {
perror("socket creation failed");
exit(EXIT_FAILURE);
}
struct sockaddr_in serverAddress;
memset(&serverAddress, 0, sizeof(serverAddress));
// Filling server information
serverAddress.sin_family = AF_INET; // IPv4
serverAddress.sin_addr.s_addr = INADDR_ANY;
serverAddress.sin_port = htons(PORT);
// Bind the socket with the server address
if(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];
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 size
buffer[bytesRecieved] = '\0';
printf("Client : %s\n", buffer);
sendto(sockfd, (const char*)responseMessage, strlen(responseMessage), MSG_CONFIRM, (const struct sockaddr*) &clientAddress, clientAddressSize);
printf("Hello message sent.\n");
return 0;
}

socketTCPServer.c

Aug 5, 2023LeifMessinger

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// 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;
}

signal() example

Nov 19, 2022CodeCatch

0 likes • 0 views

#include <stdio.h>
#include <assert.h>
#include <signal.h>
void myHandler(int iSig) {
printf("In myHandler with argument %d\n", iSig);
}
int main() {
void( * pfRet)(int) = signal(SIGINT, myHandler);
assert(pfRet != SIG_ERR);
printf("Entering an infinite loop\n");
while (1) {
printf(".");
}
return 0; // use CTRL+\ to exit
}

Fast inverse square root

Nov 19, 2022CodeCatch

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// 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;
}