I have two laptops: a Windows 10 box and a SuSE Linux box (2011-02-21 build of 2.6.37). They're on a wireless LAN and both browsing the internet via the same hub. Yet TCP doesn't work between them. What could the reasons be?
I wrote a server process that waits for a connection. I wrote a simple client process that makes that connection. When I run them on the same box, they connect fine, whether they're both on Windows or both on Linux.
However when I try to connect the client on Windows to the server on SuSE, the SuSE box does not get a connection.
Indeed when I use the utility
Test-NetConnection -ComputerName 10.226.12.12 -Port 8777, this Windows 10 standard test program also cannot connect. So that even takes my own client software out of the picture. And after trying TCP, Test-NetConnection then tries ping/ICMP and that also fails. The final report is:
WARNING: TCP connect to (10.226.12.12 : 8777) failed WARNING: Ping to 10.226.11.30 failed with status: DestinationHostUnreachable
On the SuSE box,
netstat -l shows the port 8777 is indeed being listened to.
/usr/sbin/iptables -L -v|grep policy shows
Chain INPUT (policy ACCEPT) There are no more specific rules under INPUT as I did
iptables -F INPUT. (I've also subsequently tried
iptables -I INPUT -p tcp --dport 8765 -j ACCEPT
and no improvement.)
Back to my own software, I'm giving the numeric address
gethostbyname() and that's working.
connect() I'm getting "Connection timed out."
If I set the client to connect to say
yahoo.com:80, the connection succeeds. (My software has nothing to do with HTTP; I only use this as an example of a listening port my readers will be familiar with, and to show that my laptop is indeed connected to the WiFi and able to make connections.)
Meanwhile if I run the client (it's portably-written C) on Linux, it connects to the server, so I know the port number is correct.
Looking through the Linux box's Start Menu-->Control Center-->Network Connections I am not seeing any other setting such as "don't trust my LAN" or something.
My guess is that there might be some security layer blocking this, but WHAT security?
-- would Windows 10 somehow stop me from connecting out? I have Network Profile set to "private": "for a network that you trust such as at home or work"
-- would the hub? I have no idea about it: not only am I not knowledgeable about network hardware, I am an short-term contractor... at a company renting space from a "coworking site" company that in turns rents from a bigger company renting the loft premises and doing the networking. So it'd be difficult to even find anyone who knows anything about the network hardware.
-- Would SuSE? I don't see anything on its network configuration saying something like "don't trust computers on the LAN"