Question

To develop a client/server application using TCP sockets and the C programming language that is capable of supporting multiple concurrent service requests from different clients.

PROBLEM

You are to use the Ubuntu operating system as well as both the client and the server programs. You are to modify your server program to process requests from more than one client concurrently. This means different clients may request either the same service or a total different one. The services supported by your server will include:

(1) changing all characters of a text file to uppercase, and

(2) counting the number of a supplied character in a text file.

Your client program will forward service requests to the server stating (1) the kind of service is needed, and (2) all required data necessary for the successful completion of the request. Your client program must use the following syntax for any request to the server where toUpper is the request to change characters to uppercase, and count to return how many times the supplied character is present in the file.

Your-Prompt> toUpper < file.txt >

Your-Prompt> count < char, file.txt >

In the above two examples file.txt is to indicate that a text file is to be suppled as an input parameter. Thechar string is to inform that a character is to be supplied. The information returned to the client, by your server, must be stored in text files with the names fileUpper.txt and fileChar.txt.

Answer 1

#include <process.h>
#include <netdb.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#define MAX 80
#define PORT 8080
#define SA struct sockaddr
  
// Function designed for chat between client and server.
void func(int sockfd)
{
  
char buff[MAX];
int n;
// infinite loop for chat
for (;;) {
bzero(buff, MAX);
  
// read the message from client and copy it in buffer
read(sockfd, buff, sizeof(buff));
// print buffer which contains the client contents
printf("From client: %s\t To client : ", buff);
bzero(buff, MAX);
n = 0;
// copy server message in the buffer
while ((buff[n++] = getchar()) != ' ')
;
  
// and send that buffer to client
write(sockfd, buff, sizeof(buff));
  
// if msg contains "Exit" then server exit and chat ended.
if (strncmp("toUpper", buff, 7) == 0) {
FILE *fp1, *fp2;
char a;
clrscr();

fp1 = fopen("file.txt", "r");
if (fp1 == NULL) {
puts("cannot open this file");
exit(1);
}

fp2 = fopen("fileUpper.txt", "w");
if (fp2 == NULL) {
puts("Not able to open this file");
fclose(fp1);
exit(1);
}

do {
a = fgetc(fp1);
a = toupper(a);
fputc(a, fp2);
} while (a != EOF);

fcloseall();
}
}
else{
FILE *fp;
int charcount = 0;
// Open file in read-only mode
fp = fopen(filename,"r");

// If file opened successfully, then write the string to file
if ( fp )
{
   //Repeat until End Of File character is reached.  
   while ((ch=getc(fp)) != EOF) {
      // Increment character count if NOT new line or space
       if (ch != ' ' && ch != '\n') { ++charcount; }
      
   }
}
  
fprintf(fp,"%d", charcount);
fclose(fp);
}
  
}
  
// Driver function
int main()
{
int sockfd, connfd, len;
struct sockaddr_in servaddr, cli;
  
// socket create and verification
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd == -1) {
printf("socket creation failed...\n");
exit(0);
}
else
printf("Socket successfully created..\n");
bzero(&servaddr, sizeof(servaddr));
  
// assign IP, PORT
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
servaddr.sin_port = htons(PORT);
  
// Binding newly created socket to given IP and verification
if ((bind(sockfd, (SA*)&servaddr, sizeof(servaddr))) != 0) {
printf("socket bind failed...\n");
exit(0);
}
else
printf("Socket successfully binded..\n");
  
// Now server is ready to listen and verification
if ((listen(sockfd, 5)) != 0) {
printf("Listen failed...\n");
exit(0);
}
else
printf("Server listening..\n");
len = sizeof(cli);
  
// Accept the data packet from client and verification
connfd = accept(sockfd, (SA*)&cli, &len);
if (connfd < 0) {
printf("server acccept failed...\n");
exit(0);
}
else
printf("server acccept the client...\n");
  
// Function for chatting between client and server
func(connfd);
  
// After chatting close the socket
close(sockfd);
}