Server socket not working properly while running in background - c++

Question

I have two process: Server and client. Both are different sockets. Initially I execute server socket by ./server and then ./client.
But I wanted that server process should listen in background always for the request from client.
Then inplace of executing ./server, i used ./server & . This works fine in the first client call and then when i tried to connect to server it give connection failed
server.cpp
int main(int argc, char const *argv[])
{
int server_fd, new_socket, valread;
struct sockaddr_in address;
int opt = 1;
int addrlen = sizeof(address);
char buffer[1024] = {0};
const char *hello = "Hello from server";
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_addr.s_addr = inet_addr("192.168.2.184");
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, 3) < 0)
{
perror("listen");
exit(EXIT_FAILURE);
}
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;
}
client.cpp
int main(int argc, char const *argv[])
{
int sock = 0, valread;
struct sockaddr_in serv_addr;
char *hello = "Hello from client";
char buffer[1024] = {0};
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, "192.168.2.184", &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 );
}

Answer 1

You have one misunderstanding with the bash comand lines ampersand (&) operator.
The trailing ampersand directs the shell to run the command in the background, that is, it is forked and run in a separate sub-shell, as a job, asynchronously. The shell will immediately return the return status of 0 for true and continue as normal, either processing further commands in a script or returning the cursor focus back to the user in a Linux terminal.
So, you invoke the program in the background and you can continue immediately to work in the shell.
But this does not mean that your program continues to run. When your program reaches its end, then its process will be terminated. The program stops.
So, what you could do (but definitely should not do) is, to call your program from the shell in a loop.
The correct way is, to build a loop in your server program and continue to accept connections. But then you need either to fork new processes or use a kind of factory, to create new TCP classes or whatever necessary to handle the requests from the client.
All this is not that simple, because the control flow of the program needs to be well designed. Linux has functions like (p)select, (p)poll or epoll to support with such atcivities.
There are also designpatterns like Reactor/Proactor/ACT available. You could implement that. But better to use an existing library.
But for testing purposes you approach is ok.