Traces and code from NetCheck

LICENSE

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example_apps/client_server/udp/Makefile

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+CC=gcc
+CFLAGS=-Wall -Werror -g -Wextra -Wno-unused-parameter
+
+all: udp_server udp_client
+udp_server: udp_server.o
+udp_client: udp_client.o
+
+udp_server.o: udp_server.c cnxn_constants.h
+udp_client.o: udp_client.c cnxn_constants.h
+clean:
+	-rm -rf udp_server.o udp_client.o udp_server udp_client

example_apps/client_server/udp/README.txt

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+- The 2 programs in the directory are client and server that connect and communicate
+  via UDP.
+- The purpose of these programs is to locate and obtain trace of MTU issues
+  occuring over the internet.
+- The 2 programs use constants from cnxn_constants.h to ensure that they are
+  connecting properly. The user may change these constants to alter the program.
+  See the cnxn_constants.h file for more information.
+- To build and run the program, call 'make' on the shell, and call 'make clean'
+  to remove the binary files once done using the programs.

example_apps/client_server/udp/cnxn_constants.h

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+/*
+ ** cnxn_constants.h - Constants used by UDP client and server
+ */
+
+#ifndef _CONNECTION_CONSTANTS_H_
+#define _CONNECTION_CONSTANTS_H_
+
+// the port that the client and server talk through
+#define CNXN_PORT "54453"
+
+// the message that client sends to shutdown the server
+#define SHUTDOWN_MESSAGE "done"
+
+// client sends packets based on constants below
+#define INIT_PACKET_SIZE        100
+#define MAX_PACKET_SIZE         4800
+#define PACKET_SIZE_INCREMENT   100
+
+#endif // _CONNECTION_CONSTANTS_H_

example_apps/client_server/udp/udp_client.c

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+/*
+ ** udp_client.c -- a datagram client
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <netdb.h>
+
+#include "cnxn_constants.h"
+
+// populate the servinfo structure which is a 
+// pointer to a linked list of useful network
+// information about the host
+//
+// returns non-zero error code if failed,
+//                  and zero otherwise.
+int set_servinfo(const char* hostname, struct addrinfo** servinfo) {
+	struct addrinfo hints;	
+	memset(&hints, 0, sizeof hints);
+	hints.ai_family = AF_INET; // IPv4
+	hints.ai_socktype = SOCK_DGRAM; // UDP Datagram sockets
+
+	return getaddrinfo(hostname, CNXN_PORT, &hints, servinfo);
+}
+
+// use the servinfo linkedlist to get a socket to use
+// set sockfd to the socket that we will use
+//
+// returns NULL if failed, the addrinfo of the socket if succeded
+struct addrinfo* get_socket_fd(struct addrinfo* servinfo, int* sockfd) {
+	struct addrinfo* p;
+	// loop through all the results and make a socket
+	for(p = servinfo; p != NULL; p = p->ai_next) {
+		if ((*sockfd = socket(p->ai_family, p->ai_socktype,
+						p->ai_protocol)) == -1) {
+			perror("udp_client: socket");
+			continue;
+		}
+
+		break;
+	}
+	return p;
+}
+
+// Send the shudown message to the server
+void send_shutdown_message(int sockfd, const struct addrinfo* p) {
+	int numbytes = -1;
+	if ((numbytes = sendto(sockfd, SHUTDOWN_MESSAGE, strlen(SHUTDOWN_MESSAGE), 0,
+					p->ai_addr, p->ai_addrlen)) == -1) {
+		perror("udp_client: sendto");
+		exit(1);
+	}
+	printf("udp_client: sent \"%s\" to shutdown server\n", SHUTDOWN_MESSAGE);
+}
+
+int main(int argc, char *argv[])
+{
+	struct addrinfo* p;
+	int sockfd;
+	struct addrinfo *servinfo;
+	int rv;
+	int numbytes;
+	const char* hostname = argv[1];
+
+	if (argc != 2) {
+		fprintf(stderr,"usage: %s hostname\n", argv[0]);
+		exit(1);
+	}
+
+	if ((rv = set_servinfo(hostname, &servinfo)) != 0) {
+		fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
+		return 1;
+	}
+
+	if ((p = get_socket_fd(servinfo, &sockfd)) == NULL) {
+		fprintf(stderr, "udp_client: failed to bind socket\n");
+		return 2;
+	}
+
+	// do not need servinfo anymore
+	freeaddrinfo(servinfo);
+
+	int packet_size = 0;
+	int packet_count = 0;
+	for (packet_size = INIT_PACKET_SIZE;
+			packet_size <= MAX_PACKET_SIZE;
+			packet_size += PACKET_SIZE_INCREMENT) {
+
+		packet_count++;
+		// If we have sent 10 packets already...
+		if (packet_count > 10) {
+			// resent packet_count
+			packet_count = 0;
+
+			// ... then sleep for 10 milliseconds to prevent conjestion
+			sleep(0.01);
+
+		}
+		// Fill up a buffer of size packet_size with
+		// 'a's to send a packet to server
+		char msg[packet_size];
+		memset(msg, 'a', packet_size-1);
+		msg[packet_size] = '\0';
+
+		// send the 'packet' just made to the server
+		if ((numbytes = sendto(sockfd, msg, packet_size, 0,
+						p->ai_addr, p->ai_addrlen)) == -1) {
+			perror("udp_client: sendto");
+			exit(1);
+		}
+		printf("udp_client: sent %d bytes to %s\n", numbytes, hostname);
+	}
+
+	send_shutdown_message(sockfd, p);
+	close(sockfd);
+	return 0;
+}