I am new to socket programming. My sockets work with localhost or local ip. But why can't I create a socket server with my public ip? When I try to do this in python, it complains "cannot assign requested address".
import socket
s=socket.socket()
host="address"
port=5000
s.bind((host, port))
s.listen(5)
while True:
c, addr=s.accept()
result=c.recv(1024)
print(result.decode('utf-8'))
c.send("""
test
""".encode('utf-8'))
c.close()
My IP I got from this website:http://whatismyip.host/
A service like http://whatismyip.host/ will show you the public address of your router, that is the machine that is connected to the internet. If you look up the IP of your desktop machine, it will probably show something like 192.168.0.10, with 192.168.0.1 being the address of your router that you enter in your desktop, as "gateway".
Your router resembles a firewall, separating your home network from the public internet.
In order to receive connections on your desktop machine, you would need to configure port forwarding on your router.
You will still have your python process listen on 192.168.0.10 (your local machine's IP). Or you could set it to 0.0.0.0 which is a shorthand for "all available interfaces".
Be aware that your public IP address is probably not stable.
Related
So... if i want my tcp server can be connected by other network(not just local network), i will need to setup port forwarding in my router setting page. But it's so annoying so i'm wondering is there other way to port forwarding from public IP to my local IP address.. maybe with code?
For two device both has public IP address, we can use socket IP and port to setup socket communication.
If both device do not has public IP but connect to sub-Lan then access public network through router (no port mapping in router), how can this two device setup socket connection?
For example in above diagram, how can machine A communicate with machine C?
Assuming that you have not set up a VPN tunnel between the two routers that connects both branches of the 192.168.1.0/24 network then the answer is: you can't.
If you set up a VPN tunnel then each side of the 192.168.1.0/24 network will be able to see the other side. Please note that the routers will need to be able to do ARP spoofing, i.e. the router for A & B will need to be able to spoof the MAC for C, i.e. intercept IP packages for C on their LAN and forward them through to the VPN to the other network half where they are delivered to C.
If you set up at least one port forwarding on one router, then you'll have other options, e.g. an SSH tunnel on C that connects to the port forward on either A & B. You can then use the -L option on C to setup port forwarding through the SSH tunnel to the other half of the network.
When we ping to any Public IP of a router it give a reply,
we dont get reply, if we ping a local computer with its private IP of a particular network,
So is there a way so I can make direct connection or socket with a particular PC in a network.
I have heard that, I have to make connection with public IP of a particular network and the port number will decide, on which PC in that network , my request will go.
But this method is not working..
If the computer is behind a router that uses Network Address Translation (NAT) - that is, the computer has a private IP that is not visible to the internet - then you cannot ping or establish a connection to the computer from the outside. This is because the router does not know which computer you want since all the computers behind the router share the same public IP address.
The way to establish a connection in this case is to have the computer which is behind the router establish the connection to the outside computer. For example, when you go to a web site, you can do it from a computer behind a router since your computer is initiating the connection. However, the web server you are going to must have a public IP.
When a computer behind the router initiates a connection, the router does select a port number to associate with that connection so packets from the outside for that connection will go to the right computer. However, this only works for traffic on that particular connection; the port number is not a general purpose mapping to that computer.
Two computers behind the same router can establish connections with each other using the private IPs as they don't have to go through the router to do it.
You can decide with your friend who is going to be the client (the one initiation the TCP connection) and who is the server (the one receiving the TCP connection) and which port should be used (let's say X). Let's say that your friend is the server. Then he/she has to configure his/her router to redirect all the traffic to the router to port X to his/her private IP to port X (this is what Warren mentioned as NAT).
If you use a port above 1024, the server (running on your friend's PC) doesn't need root/administrator privileges.
Your program (the client) would then connect to the public IP address of your friend. He/she can check his/her public IP with: What is my IP
I am confused about TCP/IP Socket Programming. I know the internet protocols but in theory...
I am explaining my problem (what i need )
I have a server working on X.X.X.X IP Adress. And it always listens to Y PORT.
When i want to connect that server on MY PC, i have no problem because i wrote the ip adress (X.X.X.X) and the port (Y) and my PC connects..
When i connect to server server keeps my ip adress and my local ip adress.. After that connection is end.
Here is my problem starting...
As i sad my server knows my local PC informations. How can i connect to my local PC on server my web server and sent TCP or UDP packets ? I did port forwarding on my modem but i dont want it. When i did port forwarding there is no problem but i dont want it ...
Thanks for replies and sorry for my engislih if i have mistakes .
If a router/NAT sits between your server and an outside client, you MUST use port forwarding on the router. The outside client will NOT be connecting to your server's private LAN IP/Port directly, it will be connecting to the router's public WAN IP/Port instead. So the router needs to know to forward inbound packets to that IP/Port to the server's private LAN IP/Port.
A client running on your local PC is able to connect to the server because they are both on the same LAN side of the router, so the connection is direct and does not go through the router's WAN. That is not the case for clients that are on the WAN side of the router.
I have 'Socket test v-3.0' software installed on two different PCs.
Using it can create a TCP server on 1st PC and a TCP client on 2nd PC.
When I connect both the PCs on LAN I can establish a connection & can communicate between the Server & Client.
But, When I connect both the PCs to individual Internet connections (Using dongles having different ISPs), I couldn't establish the connection between the Server & Client.
How can I do that?
Please help me out..
The private address 192.168.x.x is address that can be used for direct connection only in your private network. If you want to connect to your machine from public internet you have two options:
Get a public IP address
Configure a port forwarding
Public IP address could be get from your internet provider but it is usually requires some extra payment dependent on your service provider policy.
Port forwarding can be configured at the device at the border between your private network and internet. The device does the NAT (network address translation) between your private network and intenet. Use google if you are not sure about NAT.
Such a device can be your own device like an ADSL modem or a set top box. But such a device could be in the internet provider network. If you own the device then you can configure the port forwarding yourself. Modems usually have a web interface where you can easily configure port forwarding. See the documentation to your modem or whatever you have.
If the NAT device is in internet provider network then you have to ask it to configure port forwarding for you. Before you ask please read something about port forwarding so you are sure what you want to configure.