cmdserver: include pid of server handling requests in hello message Because unix-mode server forks child process per connection, client does not know the pid of the server that will handle requests. The pid is necessary to interrupt hung process: 1. client connects to socket server 2. server accepts the connection, forks, and tells pid 3. client requests "runcommand pull" .. hung .. 4. client sends SIGINT to the (forked) server 5. server returns from I/O wait Note that getsockopt(SO_PEERCRED) of Linux cannot be used because the server fork()s after accept().