Added c, header and make files for all assignments

assignment-2/reverse.c

@@ -0,0 +1,53 @@
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+
+static int size = 1024;
+
+void reverse(int fd) {
+	char *input = malloc(size);
+
+	int result = read(fd, input, size);
+
+	// Recursive calls until entire file is read
+	if (result > 0) {
+		reverse(fd);
+
+		// Print this chunk in reverse order
+		result--;
+		while (result >= 0) {
+			printf("%c", input[result]);
+			result--;
+		}
+
+		free(input);
+		return;
+	} else if (result == 0) {
+		free(input);
+		return;
+	} else {
+		fprintf(stderr, "ERROR: File could not be read\n");
+		free(input);
+		exit(1);
+	}
+
+}
+
+int main(int argc, char ** argv) {
+	if (argc != 2) {
+		fprintf(stderr, "Usage: reverse <file_name_to_reverse>\n");
+		return 1;
+	}
+
+	int fd = open(argv[1], O_RDONLY);
+
+	if (fd == -1) {
+		fprintf(stderr, "ERROR: File could not be opened\n");
+		return 1;
+	}
+
+	reverse(fd);
+
+	return 0;
+}

assignment-3/Makefile

@@ -0,0 +1,13 @@
+all: pingserver pingclient1 pingclient2 pingclient3
+
+pingserver: pingserver.c
+	gcc -o pingserver pingserver.c
+
+pingclient1: pingclient1.c
+	gcc -o pingclient1 pingclient1.c
+
+pingclient2: pingclient2.c
+	gcc -o pingclient2 pingclient2.c
+
+pingclient3: pingclient3.c
+	gcc -o pingclient3 pingclient3.c

assignment-3/pingclient1.c

@@ -0,0 +1,130 @@
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <netdb.h>
+#include <unistd.h>
+
+static int PORT_SERVER = 1234;
+static int SIZE = 64;
+
+int createSocket() {
+    int fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
+
+    if (fd < 0) {
+        fprintf(stderr, "ERROR: Socket could not be acquired\n");
+        exit(1);
+    }
+    return fd;
+}
+
+void sendMessage(int fd, in_addr_t s_addr) {
+    int errsend;
+    char msg[64] = "Ping test message";
+
+    struct sockaddr_in dest;
+
+    dest.sin_family = AF_INET;
+    dest.sin_port = htons(PORT_SERVER);
+    dest.sin_addr.s_addr = s_addr;
+
+    errsend = sendto(fd, msg, SIZE, 0, (struct sockaddr*) &dest, sizeof(struct sockaddr_in));
+
+    if (errsend < 0) {
+        fprintf(stderr, "ERROR: Message was not sent\n");
+        exit(1);
+    }
+}
+
+
+
+void recvMessage(int fd) {
+    char resmsg[64];
+    int errrecv;
+    socklen_t fromlen;
+    struct sockaddr_in from;
+    fromlen = sizeof(struct sockaddr_in);
+
+    errrecv = recvfrom(fd, resmsg, SIZE, 0, (struct sockaddr*) &from, &fromlen);
+
+    if (errrecv < 0) {
+        fprintf(stderr, "ERROR: Something went wrong when receiving the message\n");
+        exit(1);
+    }
+}
+
+struct in_addr * resolveHostName(const char *name) {
+    struct hostent *resolv;
+    struct in_addr *addrp;
+
+    resolv = gethostbyname(name);
+    if (resolv == NULL) {
+        fprintf(stderr, "Address not found for %s\n", name);
+        exit(1);
+    }
+
+    addrp = (struct in_addr*) resolv->h_addr_list[0];
+    return addrp;
+}
+
+struct timespec getCurrentTime() {
+    struct timespec starttime;
+    int starterr = clock_gettime(CLOCK_REALTIME, &starttime);
+    if (starterr < 0) {
+        fprintf(stderr, "ERROR: Something went wrong when reading the system clock\n");
+        exit(1);
+    }
+    return starttime;
+}
+
+double calcRTT(struct timespec starttime, struct timespec endtime) {
+    // Subtract starttime from endtime to get RTT
+    long sec = endtime.tv_sec - starttime.tv_sec;
+    long ns = endtime.tv_nsec - starttime.tv_nsec;
+
+    return ((double) sec) + ((double) ns*1E-9);
+}
+
+int main(int argc, char ** argv) {
+    // Check if there is an argument given
+    if (argc != 2) {
+        fprintf(stderr, "Usage: pingclient1 <domain-name-to-ping>\n");
+        exit(1);
+    }
+
+    int fd, err;
+    struct in_addr *addrp;
+    double rtt;
+    struct timespec starttime, endtime;
+
+    // DNS (resolving hostname)
+    addrp = resolveHostName(argv[1]);
+
+    // Create socket
+    fd = createSocket();
+
+    // Send message to the server & get start time for transmission
+    sendMessage(fd, addrp->s_addr);
+    starttime = getCurrentTime();
+
+    // Wait to receive message from server, then get the receiving/end time
+    recvMessage(fd);
+    endtime = getCurrentTime();
+
+    // Cast sec and nsec to a single double for printing
+    rtt = calcRTT(starttime, endtime);
+
+    err = printf("The RTT was: %f seconds.\n", rtt);
+    if (err < 0) {
+        exit(1);
+    }
+
+    err = close(fd);
+    if (err < 0) {
+        fprintf(stderr, "ERROR: Socket couldn't be closed");
+        exit(1);
+    }
+
+    return 0;
+}

assignment-3/pingclient2.c

@@ -0,0 +1,153 @@
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <sys/select.h>
+#include <netdb.h>
+#include <unistd.h>
+
+static int PORT_SERVER = 1234;
+static int SIZE = 64;
+
+int createSocket() {
+    int fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
+
+    if (fd < 0) {
+        fprintf(stderr, "ERROR: Socket could not be acquired\n");
+        exit(1);
+    }
+    return fd;
+}
+
+void sendMessage(int fd, in_addr_t s_addr) {
+    int errsend;
+    char msg[64] = "Ping test message";
+
+    struct sockaddr_in dest;
+
+    dest.sin_family = AF_INET;
+    dest.sin_port = htons(PORT_SERVER);
+    dest.sin_addr.s_addr = s_addr;
+
+    errsend = sendto(fd, msg, SIZE, 0, (struct sockaddr*) &dest, sizeof(struct sockaddr_in));
+
+    if (errsend < 0) {
+        fprintf(stderr, "ERROR: Message was not sent\n");
+        exit(1);
+    }
+}
+
+void recvMessage(int fd) {
+    char resmsg[64];
+    int errrecv;
+    socklen_t fromlen;
+    struct sockaddr_in from;
+    fromlen = sizeof(struct sockaddr_in);
+
+    errrecv = recvfrom(fd, resmsg, SIZE, 0, (struct sockaddr*) &from, &fromlen);
+
+    if (errrecv < 0) {
+        fprintf(stderr, "ERROR: Something went wrong when receiving the message\n");
+        exit(1);
+    }
+}
+
+struct in_addr * resolveHostName(const char *name) {
+    struct hostent *resolv;
+    struct in_addr *addrp;
+
+    resolv = gethostbyname(name);
+    if (resolv == NULL) {
+        fprintf(stderr, "Address not found for %s\n", name);
+        exit(1);
+    }
+
+    addrp = (struct in_addr*) resolv->h_addr_list[0];
+    return addrp;
+}
+
+struct timespec getCurrentTime() {
+    struct timespec starttime;
+    int starterr = clock_gettime(CLOCK_REALTIME, &starttime);
+    if (starterr < 0) {
+        fprintf(stderr, "ERROR: Something went wrong when reading the system clock\n");
+        exit(1);
+    }
+    return starttime;
+}
+
+double calcRTT(struct timespec starttime, struct timespec endtime) {
+    // Subtract starttime from endtime to get RTT
+    long sec = endtime.tv_sec - starttime.tv_sec;
+    long ns = endtime.tv_nsec - starttime.tv_nsec;
+
+    return ((double) sec) + ((double) ns*1E-9);
+}
+
+int main(int argc, char ** argv) {
+    // Check if there is an argument given
+    if (argc != 2) {
+        fprintf(stderr, "Usage: pingclient1 <domain-name-to-ping>\n");
+        exit(1);
+    }
+
+    int fd, nb, err;
+    struct in_addr *addrp;
+    struct timeval timeout;
+    struct timespec starttime, endtime;
+    double rtt = 0;
+    fd_set read_set;
+
+    // DNS (resolving hostname)
+    addrp = resolveHostName(argv[1]);
+
+    // Create socket
+    fd = createSocket();
+
+    // Send message to the server & get start time for transmission
+    sendMessage(fd, addrp->s_addr);
+    starttime = getCurrentTime();
+
+    // Specify to monitor our fd
+    FD_ZERO(&read_set);
+    FD_SET(fd, &read_set);
+
+    // Set timeout to 1 second
+    timeout.tv_sec = 1;
+    timeout.tv_usec = 0;
+
+    // Block until interrupt
+    nb = select(fd+1, &read_set, NULL, NULL, &timeout);
+
+    if (nb < 0) {
+        fprintf(stderr, "ERROR: Something went wrong with the timeout\n");
+        exit(1);
+    }
+    // If timeout occurs before packet arrives
+    if (nb == 0) {
+        err = printf("The packet was lost.\n");
+        if (err < 0) {
+            exit(1);
+        }
+    }
+    // Print RTT if packet arrived
+    if (FD_ISSET(fd, &read_set)) {
+        recvMessage(fd);
+        endtime = getCurrentTime();
+        rtt = calcRTT(starttime, endtime);
+
+        err = printf("The RTT was: %f seconds.\n", rtt);
+        if (err < 0) {
+            exit(1);
+        }
+    }
+
+    err = close(fd);
+    if (err < 0) {
+        fprintf(stderr, "ERROR: Socket couldn't be closed");
+        exit(1);
+    }
+
+    return 0;
+}