Connecting a Linux-client to MacOS-server with C - c

Question

I study sockets and try to write a very simple application. The client sends the string "Hello there!", the server accepts it, displays at itself and sends back. Wrote the client (Linux Ubuntu 18.04), and the server (macOS 10.14.2, IP: 217.144.173.149):
server:
int main()
{
int sock, listener;
struct sockaddr_in addr;
char buf[1024];
int bytes_read;
listener = socket(AF_INET, SOCK_STREAM, 0);
if(listener < 0)
{
perror("socket");
exit(1);
}
addr.sin_family = AF_INET;
addr.sin_port = htons(3425);
addr.sin_addr.s_addr = htonl(INADDR_ANY);
if(bind(listener, (struct sockaddr *)&addr, sizeof(addr)) < 0)
{
perror("bind");
exit(2);
}
listen(listener, 1);
while(1)
{
sock = accept(listener, 0, 0);
if(sock < 0)
{
perror("accept");
exit(3);
}
while(1)
{
bytes_read = recv(sock, buf, 1024, 0);
if (bytes_read <= 0) break;
printf(buf);
send(sock, buf, bytes_read, 0);
}
close(sock);
}
return 0;
}
client:
int main()
{
char message[] = "Hello there!\n";
char buf[sizeof(message)];
int sock;
struct sockaddr_in addr;
sock = socket(AF_INET, SOCK_STREAM, 0);
if(sock < 0)
{
perror("socket");
exit(1);
}
addr.sin_family = AF_INET;
addr.sin_port = htons(3425);
addr.sin_addr.s_addr = inet_addr("217.144.173.149");
if(connect(sock, (struct sockaddr *)&addr, sizeof(addr)) < 0)
{
perror("connect");
exit(2);
}
send(sock, message, sizeof(message), 0);
recv(sock, buf, sizeof(message), 0);
printf(buf);
close(sock);
return 0;
}
However, after starting the client, it just hangs and after a while gives an error: connect: Connection timed out. The server at the same time, of course, works. Google search gave no results (maybe I was looking for). What I did wrong?

Answer 1

The problem is in the way you are converting the IP address from presentation type to network type.
You should use the IP address if it is static instead of INADDR_ANY.
If the problem stays try using a different function to convert the IP.
For further reference go here.

Answer 2

As other answers suggested , please check if your server is listening on properly using netstat command in server
From the server , check if firewalld or anyfirewall specific software is running
Try using different port to bind on server , may be 8080 or something else .
I also suggest you to read the excellent guide (beejs network programming guide)
https://beej.us/guide/bgnet/

Answer 3

Check server's ipfw IP Firewall. (Open port 3425 , which is the server port listen on)
Server's IP address must be public IP. Or the server and client in the same local area network.
If you just want to test your code. You can run server and client in the same computer. Open two terminal and the one run server , the other run client. And client change the connect ip 217.144.173.149 to 127.0.0.1
127.0.0.1 mean localhost.