#include <stdio.h>
    #include <unistd.h>
    #include <stdlib.h>
    #include <string.h>
    #include <sys/types.h>
    #include <sys/socket.h>
    #include <netinet/in.h>

    char inusername[100];
    char inpassword[100];
    int pid;
    char usernames[50];
    char passwords[50];
    int Ucomp = -1000;
    int Pcomp = -1000;
    int counter = 0;
    int i = 0;
    void parser(char*, FILE*);

    void error(char *msg)
   {
perror(msg);
exit(1);
}

int main(int argc, char *argv[])
{
char input[512];

int sockfd, newsockfd, portno, clilen;
char buffer[256];
struct sockaddr_in serv_addr, cli_addr;
int n, r;
if (argc < 2)
{
    fprintf(stderr,"ERROR, no port providedn");
    exit(1);
}
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
{
    error("ERROR opening socket");
}

bzero((char *) &serv_addr, sizeof(serv_addr));
portno = atoi(argv[1]);
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(portno);
if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0)
{
      error("ERROR on binding");
}
listen(sockfd,5);
clilen = sizeof(cli_addr);
while (1)
{
    newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen);
    puts("Connection accepted");
    pid = fork();
    if (pid < 0) {
        error("ERROR in creating new socket");
    }
    if (pid == 0) {
        close(sockfd);
        while (counter <= 3)
        {
            FILE *pToFile = fopen("pwd.txt", "r");

            write(newsockfd, "Username:", strlen("Usernamen"));
            recv(newsockfd, inusername, 20, 0);

            write(newsockfd, "Password:", strlen("Passwordn"));
            recv(newsockfd, inpassword, 20, 0);

            parser(input, pToFile);

            if (Ucomp == 0)
            {

                if (Pcomp == 0)
                {
        write(newsockfd, "Welcome to chat", strlen("Welcome to chatn"));
        close(newsockfd);
        exit(1);
                }
            }
            else if (counter < 2)
            {

                write(newsockfd, "InvalidnUsername:", strlen("Invalid"));
                memset(&inusername[0], 0, sizeof(inusername));
                memset(&inpassword[0], 0, sizeof(inpassword));
                counter++;
            }
            else
            {

            write(newsockfd, "Access Denied", strlen("Access Deniedn"));
            exit(1);
            close(newsockfd);

            }

            fclose(pToFile);
        }
    }
    else {
        close(newsockfd);
    }
}

return 0;
}

void parser(char *input, FILE *pToFile)
 {
int pCounter = 0;
char * pch;

while (fgets(input, 512, pToFile))
{
    pch = strtok(input, " ");

    while (pch != NULL)
    {
        if (Ucomp == 0 && Pcomp == 0)
        {
            return;
        }

        if (pCounter == 0)
        {
            strcpy(usernames, pch);

            Ucomp = strcmp(inusername, usernames);

        }
        else if (pCounter == 1)
        {
            strcpy(passwords, pch);

            Pcomp = strcmp(inpassword, passwords);

        }
        else if (pCounter == 4)
        {
            pCounter = -1;
        }


        pch = strtok(NULL, " ");

        pCounter++;
    }

    if (Ucomp == 0 && Pcomp == 0)
    {
        return;
    }
}
 }

#include <stdio.h>
    #include <sys/types.h>
    #include <sys/socket.h>
    #include <netinet/in.h>
    #include <netdb.h>
    #include <stdlib.h>
    #include <string.h>
    #include <unistd.h>
    #include <fcntl.h>

    char reply[100], message[2000];
    int counter = 1;

    void error(char *msg)
    {
      perror(msg);
      exit(0);
    }

     int main(int argc, char *argv[])
  {
int sockfd, portno, n, r;
char buffer[256];

struct sockaddr_in serv_addr;
struct hostent *server;

if (argc < 3)
{
    fprintf(stderr,"usage %s hostname portn", argv[0]);
    exit(0);
}

portno = atoi(argv[2]);
sockfd = socket(AF_INET, SOCK_STREAM, 0);

if (sockfd < 0)
{
    error("ERROR opening socket");
}

server = gethostbyname(argv[1]);

if (server == NULL)
{
    fprintf(stderr,"ERROR, no such hostn");
    exit(0);
}

bzero((char *) &serv_addr, sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
bcopy((char *)server->h_addr, (char *)&serv_addr.sin_addr.s_addr, server->h_length);
serv_addr.sin_port = htons(portno);

if (connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0)
{
    error("ERROR connecting");
}

while(1)
{
    recv(sockfd,reply,2000,0);
    puts(reply);

    if (counter == 3)
    {
        recv(sockfd, reply, 2000, 0);
        puts(reply);
        counter++;
    }
    else if (counter == 6)
    {
        recv(sockfd, reply, 2000, 0);
        puts(reply);
        counter++;
    }
    else if (counter == 9)
    {
        close(sockfd);
        break;
    }
    counter++;
    scanf("%s",message);
    send(sockfd,message,strlen(message),0);.
    memset(&reply[0], 0, sizeof(reply));
}
return 0;
  }