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socat

Working with socat to send a message and receive a response

Using Socat on my server I have the current command:

socat -u tcp-l:7767,fork system:/app/getmsg.sh

All getmsgh.sh does is:

read MESSAGE
echo $MESSAGE

I'm trying to figure out a way for the client to send a message and receive the output of getmsg.sh

Trying on the client:

echo "hello" | socat -t 30 tcp:localhost:7767 -

Does not seem to work. It shows up on the server but not on the client. It seems that if you try to pass a message with the client socat wants to exit immediately

Solution

  • The problem is the -u option on the server side. The meaning of the -u option from the socat man page:

    Uses unidirectional mode. The first address is only used for reading, and the second address is only used for writing

    Hence, the tcp-l: side is only read from and the system: side is only written to, instead of a bi-directonal connection (which is the default). Removing the -u option makes the example in the question work.