the concurrent server, Here, Client A has already established a connection with the server, which has then created a child server process to handle the transaction. This allows the server to process Client B’s request without waiting for A’s transaction to complete. More than one child server can be started in this way.
TCP Echo Client
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>
#include <arpa/inet.h>
#define MAXLINE 4096 /*max text line length*/
#define SERV_PORT 3000 /*port*/
int
main(int argc, char **argv)
{
int sockfd;
struct sockaddr_in servaddr;
char sendline[MAXLINE], recvline[MAXLINE];
//basic check of the arguments
//additional checks can be inserted
if (argc !=2) {
perror("Usage: TCPClient <IP address of the server");
exit(1);
}
//Create a socket for the client
//If sockfd<0 there was an error in the creation of the socket
if ((sockfd = socket (AF_INET, SOCK_STREAM, 0)) <0) {
perror("Problem in creating the socket");
exit(2);
}
//Creation of the socket
memset(&servaddr, 0, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr= inet_addr(argv[1]);
servaddr.sin_port = htons(SERV_PORT); //convert to big-endian order
//Connection of the client to the socket
if (connect(sockfd, (struct sockaddr *) &servaddr, sizeof(servaddr))<0) {
perror("Problem in connecting to the server");
exit(3);
}
while (fgets(sendline, MAXLINE, stdin) != NULL) {
send(sockfd, sendline, strlen(sendline), 0);
if (recv(sockfd, recvline, MAXLINE,0) == 0){
//error: server terminated prematurely
perror("The server terminated prematurely");
exit(4);
}
printf("%s", "String received from the server: ");
fputs(recvline, stdout);
}
exit(0);
}
TCP Concurrent Echo Server
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>
#include <unistd.h>
#define MAXLINE 4096 /*max text line length*/
#define SERV_PORT 3000 /*port*/
#define LISTENQ 8 /*maximum number of client connections*/
int main (int argc, char **argv)
{
int listenfd, connfd, n;
pid_t childpid;
socklen_t clilen;
char buf[MAXLINE];
struct sockaddr_in cliaddr, servaddr;
//Create a socket for the soclet
//If sockfd<0 there was an error in the creation of the socket
if ((listenfd = socket (AF_INET, SOCK_STREAM, 0)) <0) {
perror("Problem in creating the socket");
exit(2);
}
//preparation of the socket address
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
servaddr.sin_port = htons(SERV_PORT);
//bind the socket
bind (listenfd, (struct sockaddr *) &servaddr, sizeof(servaddr));
//listen to the socket by creating a connection queue, then wait for clients
listen (listenfd, LISTENQ);
printf("%s\n","Server running...waiting for connections.");
for ( ; ; ) {
clilen = sizeof(cliaddr);
//accept a connection
connfd = accept (listenfd, (struct sockaddr *) &cliaddr, &clilen);
printf("%s\n","Received request...");
if ( (childpid = fork ()) == 0 ) {//if it’s 0, it’s child process
printf ("%s\n","Child created for dealing with client requests");
//close listening socket
close (listenfd);
while ( (n = recv(connfd, buf, MAXLINE,0)) > 0) {
printf("%s","String received from and resent to the client:");
puts(buf);
send(connfd, buf, n, 0);
}
if (n < 0)
printf("%s\n", "Read error");
exit(0);
}
//close socket of the server
close(connfd);
}
}