Question

I am working on a server/client based project. I almost finished my server side code.

I develop the server app in EclipseCDT on Ubuntu Desktop, and everything just works fine.

But when deploy my app to a Ubuntu Server (I tried Server 10.04/10.10), the server app can start normally (waiting for connection), but the same client just cannot connect to the server.

I use Socket for receiving and sending data to/from the client.

Peter

P.S.: if I install sudo apt-get install ubuntu-desktop on my server machine, then everything works fine again.

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New Findings from the source code:

LabelStartBlocking:
int newScoketId = ::accept(socketId, 0, 0); // socketId == 3 ::accept is define in socket.h
                          // waiting for connection
LabelResume: // if new connection coming
// Do something with newSocketId

The behavior difference between Ubuntu Desktop and Server is:

On Ubuntu Desktop version, when the server starts, it is blocked at LabelStartBlocking with the socket routine ::accept; and then if a new connection arrives, the server will resume at LabelResume and create a new socket connection using the return value newSocketId;

However, on Ubuntu Server version, when the server starts, it is also blocked at LabelStartBlocking with the socket routine ::accept, but if a new connection arrives, the server won’t resume at LabelResume, and the new socket connection CANNOT be created.

Can you guys help me out?

Peter

Answer 1

Thanks for your attention.

I finally figured it out.

If there are more than one IP addresses for the same hostname (/etc/hosts), the old code will fail.

Example /etc/hosts file:

127.0.0.1 localhost YourHostName
10.50.10.251 YourHostName

I traced the calling stack, and I found that, the IP address (10.50.10.251) passed to the program is translated into hostname, and then later the hostname is translated back to IP address (for binding), but a DIFFERENT one, that’s why my server program cannot accept any client connection.

Hope it helps if any others have the similar issue.

Peter