Minimal web server using netcat

Question

Try this:

while true ; do nc -l -p 1500 -c 'echo -e "HTTP/1.1 200 OK\n\n $(date)"'; done

The -cmakes netcat execute the given command in a shell, so you can use echo. If you don't need echo, use -e. For further information on this, try man nc. Note, that when using echo there is no way for your program (the date-replacement) to get the browser request. So you probably finally want to do something like this:

while true ; do nc -l -p 1500 -e /path/to/yourprogram ; done

Where yourprogram must do the protocol stuff like handling GET, sending HTTP 200 etc.

Donno how or why but i manage to find this around and it works for me, i had the problem I wanted to return the result of executing a bash

$ while true; do { echo -e 'HTTP/1.1 200 OK\r\n'; sh test; } | nc -l 8080; done

NOTE: This command was taken from: http://www.razvantudorica.com/08/web-server-in-one-line-of-bash

this executes bash script test and return the result to a browser client connecting to the server running this command on port 8080

My script does this ATM

$ nano test

#!/bin/bash

echo "************PRINT SOME TEXT***************\n"
echo "Hello World!!!"
echo "\n"

echo "Resources:"
vmstat -S M
echo "\n"

echo "Addresses:"
echo "$(ifconfig)"
echo "\n"


echo "$(gpio readall)"

and my web browser is showing

************PRINT SOME TEXT***************

Hello World!!!


Resources:
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
 0  0      0    314     18     78    0    0     2     1  306   31  0  0 100  0


Addresses:
eth0      Link encap:Ethernet  HWaddr b8:27:eb:86:e8:c5  
          inet addr:192.168.1.83  Bcast:192.168.1.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:27734 errors:0 dropped:0 overruns:0 frame:0
          TX packets:26393 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:1924720 (1.8 MiB)  TX bytes:3841998 (3.6 MiB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)


GPIOs:
+----------+-Rev2-+------+--------+------+-------+
| wiringPi | GPIO | Phys | Name   | Mode | Value |
+----------+------+------+--------+------+-------+
|      0   |  17  |  11  | GPIO 0 | IN   | Low   |
|      1   |  18  |  12  | GPIO 1 | IN   | Low   |
|      2   |  27  |  13  | GPIO 2 | IN   | Low   |
|      3   |  22  |  15  | GPIO 3 | IN   | Low   |
|      4   |  23  |  16  | GPIO 4 | IN   | Low   |
|      5   |  24  |  18  | GPIO 5 | IN   | Low   |
|      6   |  25  |  22  | GPIO 6 | IN   | Low   |
|      7   |   4  |   7  | GPIO 7 | IN   | Low   |
|      8   |   2  |   3  | SDA    | IN   | High  |
|      9   |   3  |   5  | SCL    | IN   | High  |
|     10   |   8  |  24  | CE0    | IN   | Low   |
|     11   |   7  |  26  | CE1    | IN   | Low   |
|     12   |  10  |  19  | MOSI   | IN   | Low   |
|     13   |   9  |  21  | MISO   | IN   | Low   |
|     14   |  11  |  23  | SCLK   | IN   | Low   |
|     15   |  14  |   8  | TxD    | ALT0 | High  |
|     16   |  15  |  10  | RxD    | ALT0 | High  |
|     17   |  28  |   3  | GPIO 8 | ALT2 | Low   |
|     18   |  29  |   4  | GPIO 9 | ALT2 | Low   |
|     19   |  30  |   5  | GPIO10 | ALT2 | Low   |
|     20   |  31  |   6  | GPIO11 | ALT2 | Low   |
+----------+------+------+--------+------+-------+

simply amazing!

Add -q 1 to the netcat command line:

while true; do 
  echo -e "HTTP/1.1 200 OK\n\n $(date)" | nc -l -p 1500 -q 1
done

The problem you are facing is that nc does not know when the web client is done with its request so it can respond to the request.
A web session should go something like this.

TCP session is established.
Browser Request Header: GET / HTTP/1.1
Browser Request Header: Host: www.google.com
Browser Request Header: \n #Note: Browser is telling Webserver that the request header is complete.
Server Response Header: HTTP/1.1 200 OK
Server Response Header: Content-Type: text/html
Server Response Header: Content-Length: 24
Server Response Header: \n #Note: Webserver is telling browser that response header is complete 
Server Message Body: <html>sample html</html>
Server Message Body: \n #Note: Webserver is telling the browser that the requested resource is finished. 
The server closes the TCP session.

Lines that begin with "\n" are simply empty lines without even a space and contain nothing more than a new line character.

I have my bash httpd launched by xinetd, xinetd tutorial. It also logs date, time, browser IP address, and the entire browser request to a log file, and calculates Content-Length for the Server header response.

user@machine:/usr/local/bin# cat ./bash_httpd
#!/bin/bash
x=0;
Log=$( echo -n "["$(date "+%F %T %Z")"] $REMOTE_HOST ")$(
        while read I[$x] && [ ${#I[$x]} -gt 1 ];do
              echo -n '"'${I[$x]} | sed -e's,.$,",'; let "x = $x + 1";
        done ;
); echo $Log >> /var/log/bash_httpd

Message_Body=$(echo -en '<html>Sample html</html>')
echo -en "HTTP/1.0 200 OK\nContent-Type: text/html\nContent-Length: ${#Message_Body}\n\n$Message_Body"

To add more functionality, you could incorporate.

            METHOD=$(echo ${I[0]} |cut -d" " -f1)
            REQUEST=$(echo ${I[0]} |cut -d" " -f2)
            HTTP_VERSION=$(echo ${I[0]} |cut -d" " -f3)
            If METHOD = "GET" ]; then 
                case "$REQUEST" in

                    "/") Message_Body="HTML formatted home page stuff"
                        ;;
                    /who) Message_Body="HTML formatted results of who"
                        ;;
                    /ps) Message_Body="HTML formatted results of ps"
                        ;;
                    *) Message_Body= "Error Page not found header and content"
                       ;;
                esac

            fi

Happy bashing!

Another way to do this

while true; do (echo -e 'HTTP/1.1 200 OK\r\n'; echo -e "\n\tMy website has date function" ; echo -e "\t$(date)\n") | nc -lp 8080; done

Let's test it with 2 HTTP request using curl

In this example, 172.16.2.6 is the server IP Address.

Server Side

admin@server:~$ while true; do (echo -e 'HTTP/1.1 200 OK\r\n'; echo -e "\n\tMy website has date function" ; echo -e "\t$(date)\n") | nc -lp 8080; done

GET / HTTP/1.1 Host: 172.16.2.6:8080 User-Agent: curl/7.48.0 Accept:
*/*

GET / HTTP/1.1 Host: 172.16.2.6:8080 User-Agent: curl/7.48.0 Accept:
*/*

Client Side

user@client:~$ curl 172.16.2.6:8080

        My website has date function
        Tue Jun 13 18:00:19 UTC 2017

user@client:~$ curl 172.16.2.6:8080

        My website has date function
        Tue Jun 13 18:00:24 UTC 2017

user@client:~$

If you want to execute another command, feel free to replace $(date).

I had the same need/problem but nothing here worked for me (or I didn't understand everything), so this is my solution.

I post my minimal_http_server.sh (working with my /bin/bash (4.3.11) but not /bin/sh because of the redirection):

rm -f out
mkfifo out
trap "rm -f out" EXIT
while true
do
  cat out | nc -l 1500 > >( # parse the netcat output, to build the answer redirected to the pipe "out".
    export REQUEST=
    while read -r line
    do
      line=$(echo "$line" | tr -d '\r\n')

      if echo "$line" | grep -qE '^GET /' # if line starts with "GET /"
      then
        REQUEST=$(echo "$line" | cut -d ' ' -f2) # extract the request
      elif [ -z "$line" ] # empty line / end of request
      then
        # call a script here
        # Note: REQUEST is exported, so the script can parse it (to answer 200/403/404 status code + content)
        ./a_script.sh > out
      fi
    done
  )
done

And my a_script.sh (with your need):

#!/bin/bash

echo -e "HTTP/1.1 200 OK\r"
echo "Content-type: text/html"
echo

date