[cs631apue] why does fd 4 get re-used?

[jphillip]

Accept returns me a fd of 4.  I fork a child to handle the connection 
and in that child I call the open command to read from the requested 
file.  Open also returns a fd of 4 and I can no longer send a reply to 
the socket which had fd 4.  Any ideas why?  here is some debug from my 
program:

[file request.c, line 238]: Reading request from socket 4
[file request.c, line 295]: Received GET request
[file request.c, line 308]: DECODED URI=t1/xyz
[file request.c, line 352]: Got full request version 1.0
[file response.c, line 101]: REQUEST FOR HTTP FILE: 
/home/jphillip/Final/sws/t1/xyz
[file response.c, line 35]: Open resource for read-only, open returned 
fd=4
[file response.c, line 41]: allocated read buf of size 1048576 bytes
[file response.c, line 47]: read 27 bytes from file: THIS IS THE FILE 
CONTENTS


[file response.c, line 70]: failed to write 27 bytes of file data to 
socket fd 4: Bad file descriptor