Error explanations
TCP/IP errors

There are some TCP/IP error with explanation:

10048 WSAEADDRINUSE
Required address (port number) is already in use. It occurs when application try to bind socket to specified IP address and port. In normal cases only one socket may be bound to the one port.
This error may occur when you are starting P+ and another proxy or mail server is already started. When you define multiple Mapped Links with the same "Proxy Port" number you will find this error message in ErrLog file.
You can obtain used port numbers using netstat.exe program from DOS Prompt. See this article.

10051 WSAEANETUNREACH
10065 WSAEHOSTUNREACH
Destination IP address is unreachable.
These errors occur when target server doesn't exist or link to server doesn't exist (broken lines, server down,..).

10055 WSAENOBUFS
Windows system has no memory for TCP/IP buffers. More information see this article.

10060 WSAETIMEDOUT
Connection establishing (or another action) was not finished before assigned time expired.

10061 WSAECONNREFUSED
Target server rejects connection attempt due to security settings.