TCP/IP server using c - c

Question

I want to make a server-client programm.The first thing i can't find is to make the server never shut down and accept each client.I put a while(1) on my server to run but after 3 connections to one client my server stops accepting other connections and i delete this while.I cant find how to build this think.Also i want to create TCP/IP socket so am i making the socket with the right way?
Im working on ubuntu at Visual Studio Code.
Server:
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#define PORT 8080
int main(int argc,char* argv[]){
int server_fd, new_socket, valread;
struct sockaddr_in address;
int opt = 1;
int addrlen = sizeof(address);
char *hello = "Hello from server";
while(1){
char buffer[1024] = {0};
printf("Server\n");
// Creating socket file descriptor
if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {
perror("socket failed");
exit(EXIT_FAILURE);
}
// Forcefully attaching socket to the port 8080
if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT,&opt,
sizeof(opt))) {
perror("setsockopt");
exit(EXIT_FAILURE);
}
address.sin_family = AF_INET;
address.sin_addr.s_addr = INADDR_ANY;
address.sin_port = htons( PORT );
// Forcefully attaching socket to the port 8080
if (bind(server_fd, (struct sockaddr *)&address,sizeof(address))<0) {
perror("bind failed");
exit(EXIT_FAILURE);
}
if (listen(server_fd, 1) < 0) {
perror("listen");
exit(EXIT_FAILURE);
}
printf("Listening...\n");
if ((new_socket = accept(server_fd, (struct sockaddr *)&address,(socklen_t*)&addrlen))<0) {
perror("accept");
exit(EXIT_FAILURE);
}
valread = read( new_socket , buffer, 1024);
printf("%s\n",buffer );
send(new_socket , hello , strlen(hello) , 0 );
printf("Hello message sent\n");
}
return 0;
}
My client so far:
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>
#define PORT 8080
int main(int argc,char* argv[]){
char* command = (char*) malloc(15*sizeof(char));
int sock = 0, valread;
struct sockaddr_in serv_addr;
char *hello = "Hello from client";
char buffer[1024] = {0};
printf("Client\n");
if ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0){
printf("\n Socket creation error \n");
return -1;
}
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(PORT);
// Convert IPv4 and IPv6 addresses from text to binary form
if(inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr)<=0) {
printf("\nInvalid address/ Address not supported \n");
return -1;
}
if (connect(sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) {
printf("\nConnection Failed \n");
return -1;
}
send(sock , hello , strlen(hello) , 0 );
printf("Hello message sent\n");
valread = read( sock , buffer, 1024);
printf("%s\n",buffer );
return 0;
}

Answer 1

You have to put the loop only around the code, which accepts the clients. The server socket itself is only created once.
// Creation of server socket(), bind(), listen()
while (1) {
if ((new_socket = accept(server_fd, (struct sockaddr *)&address,
(socklen_t*)&addrlen)) < 0) {
perror("accept");
exit(EXIT_FAILURE);
}
valread = read( new_socket , buffer, 1024);
printf("%s\n",buffer );
send(new_socket , hello , strlen(hello) , 0 );
printf("Hello message sent\n");
}
Furthermore, you should close the client socket at the end of the while block after the communication is finished (i.e. after the printf("Hello message sent\n");:
close(new_socket);
And note, that the clients are served serially this way. They can connect concurrently, but only one client is served at a time. If you need concurrent handling, you can for example fork() several processes, each handling one client, or handle multiple clients in one thread using poll() or select().