Python sockets/port forwarding

I've written server and client programs with Python.

Server.py

import socket

sock = socket.socket (socket.AF_INET, socket.SOCK_STREAM)

host = socket.gethostname()
port = 5555

sock.bind((host, port))

sock.listen(1)

conn, addr = sock.accept()

data = "Hello!"
data = bytes(data, 'utf-8')

conn.send(data)

sock.close()

Client.py on Linux

import socket

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

host = socket.gethostname()
port = 5555

sock.connect((host, port))

data = sock.recv(2048)

data = str(data, "utf-8")

print(data)

sock.close()

When I run the server and then the client on my local machine (a Linux Mint), it works correctly. I got "Hello!" in bash, and everything is fine. BUT when I ran my client program on another machine (a Windows 8) and ran it (previously I ran server on Linux, of course, and change IP address in client to my static Linux mint's IP) it says:

ConnectionRefusedError: [WinError 10061] No connection could be made because the target machine actively refused it

client.py on Windows

import socket
    
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    
host = "here is my static ip"
port = 5555
    
sock.connect((host, port))
    
data = sock.recv(2048)
    
data = str(data, "utf-8")
    
print(data)
    
sock.close()

I must say that I had done port forwarding in my router settings on port 5555. Earlier, I had done same thing to port 80 and my own site worked correctly, but now it doesn't work to 5555 with Python sockets! Why? I can't get it! And one more thing: I tried to change the port to 80 in my server and client files, but it didn't work too. PLease, help.