Python Socket to connect over Global Public IP Address

Question

I have been working on a project to connect computers located in different locations together through Python. Initially, while testing, I used my private IP address (I did not know it was private at the time) to connect computers on the same network as mine. But as soon as I tried doing this with computers located on different networks in different locations, it simply did not work.

And I assume this is because the program is using the local IP address of my computer that can connect only to computers on the same network. Here are my simplified programs:

Here is my server-side script:

server = socket.gethostbyname(socket.gethostname()) # 10.128.X.XXX which is the Internal IP
print(server)
port = 5555
clients = 0

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((server, port))

s.listen(2)
print("Waiting for connection...")

while True:
    conn, addr = s.accept()
    print("Connected to: ", addr)

    conn.send(str.encode(f"{clients}"))
    clients += 1

and here is my client side-script:

class Network:
    def __init__(self):
        self.client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.server = "10.128.0.2"
        self.port = 5555
        self.addr = (self.server, self.port)
        self.id = int(self.connect())

    def connect(self):
        self.client.connect(self.addr)
        return self.client.recv(2048).decode()

network = Network()
print(f"Connected as client {network.id}")

Now when I tried replacing the private IP address with the global IP address (as specified here: How do I get the external IP of a socket in Python?) I got the following error:

# Getting the Global IP Address

from requests import get
server = get("https://api.ipify.org").text

s.bind((server, port))
OSError: [WinError 10049] The requested address is not valid in its context

I have tried searching a lot on how to communicate (transfer small amounts of data as strings) between multiple computers located in different locations using different networks, but I haven't really gotten a solution. Is there a way that I can do this?

Answer 1

In server you always use local IP (it is IP of one of network cards in computer or 0.0.0.0 to use all network cards)

s.bind( (local_IP, port) )

# or 

s.bind( ('0.0.0.0', port) ) 

In client you use external IP

s.connect( (external_IP, port) )

---

External client uses external IP to connect with your Internet Provider route and this router knows that this external IP is assigned to your computer and it redirects it your server.

At the same time local client can use local IP to connect with the same server.

external_client --> router(external_IP) --> server(local_IP) <-- local_client