Java套接字连接被拒绝

Question

I am trying to run the "GreetingClient" code from the following page: http://www.tutorialspoint.com/java/java_networking.htm

The servername is being set to "localhost" and port 80. With these parameters I am able to run the program without any exceptions, but the code spins when it gets to in.readUTF() line.

When the port is changed to any other port, I get a connection refused exception.

On the other hand, when I create a simple "ServerSocket" program that receives requests on port 80, I get "Address already in use" exception, any port other than 80 works for the "ServerSocket" code.

I have Red hat enterprise web server installed locally that uses port 80, but it is shutdown and does not run when these program are running.

Doing telnet gives me the following results:

1. telent localhost 80: Connection is not refused
2. telnet localhost 81 (or any other port other than 80): Connecting To localhost...Could not open connection to the host, on port 81: Connect failed

I have telnet client feature turned on.

Answer 1

What you're doing doesn't make sense. Clients and servers go together. You can't connect any arbitrary client to any arbitrary server. They have to speak the same protocol, in this case a request/reply using writeUTF() and readUTF().

This code will only work when connecting to the corresponding server in the same link. You can't connect it to port 80, which is an HTTP server, not the GreetingServer, and expect it to work. It's not an HTTP client, it is a client of its own server. A telnet server won't work either, nor will aa Telnet client when connected to the GreetingServer.

'Connection refused' means there is nothing listening at that IP:port.

You need to run the GreetingServer on some port and next the client to that.

NB Curious code. The server catches a SocketTimeoutException that is never thrown.