I remember trying to write a web server that can respond to requests in bash, several years ago. Since it didn't have sockets support that part was going to be handled by netcat. The problem I ended up with was that bash couldn't read and write to the same pipe. The mkfifo solution was the closest that I got to. It turns out that ksh was perfectly capable of reading and writing to the same pipe at that stage. Not long after I got stuck with bash, awk started to support sockets so I used that. Then bash started to support sockets, and many more features, so I suspect it's possible to write a solution in bash now that doesn't need netcat, but might still need a fifo.