Network Programming--client returns connect refused and no route to host__ programming

Just contact the network programming, groping and pass the program,
Often encountered by the Connect function thrown
Connect refused and no route to host these two issues
Summing up,

Connect refused is mainly due to the connection of the sockaddr_in configuration is incorrect, that is, IP filled out the wrong or wrong port, resulting in errors

No route to host this time if the IP fill loop (127.0.0.1) No problem, but once you write the IP of this machine, there is no route to host this connection error
Try to turn off the firewall and discover that the latter is caused by a firewall with no open ports

Service Firewalld Stop