Something

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <arpa/inet.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <linux/if.h>
#include <linux/if_packet.h>
#include <linux/if_ether.h>
#include <sys/wait.h>
#include <sys/time.h>

void printError(char msg[128]);
void transmit(int port, int protocol, int requests, int buffersize);

struct sockaddr_in remote_addr;
struct ifreq ifreq;
socklen_t s_size;
FILE* logfile;

int main(int argc, char* argv[]) {
	pid_t pid;
	int i, port, clients, requests, buffersize, protocol;

	if (argc < 7) printError("usage: testcli <ip> <port> <protocol> <clients> <requests> <bytes>\n");

	logfile = fopen("log.txt","w");

	if (inet_addr(argv[1]) == -1) printError("invalid ip address\n");
	if ((port = atoi(argv[2])) < 1) printError("port < 1\n");
	if ((clients = atoi(argv[4])) < 1) printError("clients < 1\n");
	if ((requests = atoi(argv[5])) < 1) printError("requests < 1\n");
	if ((buffersize = atoi(argv[6])) < 1 || buffersize > 8192) printError("bytes parameter must be between 1 and 8192\n");
	if (!strcmp(argv[3],"UDP")) protocol = SOCK_DGRAM;
	else if (!strcmp(argv[3],"TCP")) protocol = SOCK_STREAM;
	else printError("invalid protocol specified");

	remote_addr.sin_family = AF_INET;
	remote_addr.sin_port = htons(port);
	inet_pton(AF_INET, argv[1], &remote_addr.sin_addr.s_addr);

	strcpy (ifreq.ifr_name, "eth0");
	s_size = sizeof(remote_addr);

	if (getpid() == getppid()) {
		fprintf(logfile,"LOG: %i bytes\n", buffersize);
		fprintf(logfile,"LOG: %i clients\n", clients);
		fprintf(logfile,"-------------------\n");
	}

	for (i = 0; i < clients; i++) {
		pid = fork();
		switch(pid) {
			case -1: printError("Fork error\n");
			case 0: {
				transmit(port, protocol, requests, buffersize);
				break;
			}
		}
	}
	for (i = 0; i < clients; i++) wait(0);

	fclose(logfile);
	return 0;
}

void transmit(int port, int protocol, int requests, int buffersize) {
	int i, sock, msec;
	char buffer[buffersize], rbuffer[buffersize];
	
	for (i = 0; i < buffersize; i++) { buffer[i] = (char)(rand() % 92 + 70); }

	struct timeval start, finish;
  	gettimeofday (&start, NULL);
	switch (protocol) {
		case SOCK_STREAM:{
			if ((sock = socket(AF_INET, protocol, 0)) == -1) printError("Can't create socket\n");
			if (connect(sock, (struct sockaddr *)&remote_addr, s_size) == -1) printError("Can't connect\n");
			printf("Forked TCP process (pid: %i) connected\n", getpid());
			for (i = 0; i < requests; i++) {
				if (send(sock, buffer, buffersize, 0) == -1) printf("Forked process, Send error (pid: %i)\n", getpid());
				if (recv(sock, rbuffer, buffersize, 0) == -1) printf("Forked process, Recv error (pid: %i)\n", getpid());
				else printf("Forked process %i sent:	%s\n		received:	%s\n", getpid(), buffer, rbuffer);
			}
			close(sock);
			gettimeofday (&finish, NULL);
			msec = finish.tv_sec * 1000 + finish.tv_usec / 1000;
	  		msec -= start.tv_sec * 1000 + start.tv_usec / 1000;
			printf("Forked process (pid: %i) killed\n", getpid());
			fprintf(logfile," - Duration: %5.3fs\n", (double)msec/1000);
			exit(0);
			break;
		}
		case SOCK_DGRAM:{
			if ((sock = socket(AF_INET, protocol, 0)) == -1) printError("Can't create socket\n");
			printf("Forked UDP process (pid: %i) created\n", getpid());
			for (i = 0; i < requests; i++) {
				if (sendto(sock, buffer, buffersize, 0, (struct sockaddr*)&remote_addr, s_size) == -1) printf("Forked process, Sendto error (pid: %i)\n", getpid());
				if (recvfrom(sock, rbuffer, buffersize, 0, (struct sockaddr*)&remote_addr, &s_size) == -1) printf("Forked process, Recvfrom error (pid: %i)\n", getpid());
				else printf("Forked process %i sent:	%s\n		received:	%s\n", getpid(), buffer, rbuffer);
			}
			close(sock);
			gettimeofday (&finish, NULL);
			msec = finish.tv_sec * 1000 + finish.tv_usec / 1000;
	  		msec -= start.tv_sec * 1000 + start.tv_usec / 1000;
			printf("Forked process (pid: %i) killed\n", getpid());
			fprintf(logfile," - Duration: %5.3fs\n", (double)msec/1000);
			exit(0);
			break;
		}
	}
}
void printError(char msg[128]) {
	printf(msg);
	exit(1);
}