socat/FAQ

Q: What is the clue of socat?

A: socat probably doesn't have any clue. It is more an attempt to smoothly
integrate similar I/O features that are usually handled differently under
UNIX.


Q: What does the prefix XIO mean?

A: XIO means "extended input/output". It is a library/API that provides a
common way for handling files, sockets and other forms of I/O. Its advantage is
that the application may reduce its I/O to open / read+write / close calls,
while the user controls all I/O details (and even basic process properties) by
packing options into the filename string. This is the basic part of socat.


Q: Is there a Windows port of socat available?

A: Try with Cygwin from http://www.cygwin.com/, or upgrade to Linux.


Q: I succeeded to configure and make socat, but ./test.sh says something
like:
./test.sh: No such file or directory

A: You need a bash shell, and its location must be correctly specified in the
first line of test.sh, e.g. /usr/local/bin/bash instead of /bin/bash.


Q: configure disables readline / openssl / libwrap support because it does not
find an include file / the library. How can I tell configure where these files
are?

A: For include locations, use the environment variable CPPFLAGS, for library
locations use LIBS, e.g.:
   export CPPFLAGS="-I/home/user/ssl/include"
   export LIBS="-L/home/user/ssl/lib"
On some systems (SunOS), you might also need to set LD_LIBRARY_PATH:
   export LD_LIBRARY_PATH="$LD_LIBRARY_PATH:/home/user/ssl/lib"
Then try again:
   make distclean; ./configure; make


Q: I succeeded to make socat, but the test.sh script fails for many tests.
Is my socat build corrupt?

A: Probably your socat program is ok; the tests have been developed on Linux
2.4, and there they usually succeed.
But the following OS differences result in errors on non Linux systems:
 * Linux allows to bind a socket to any address of range 127.0.0.0/8, not
   only 127.0.0.1. Some tests are built on this feature, but they might fail on
   other systems. 
 * Your OS might have no IP6 implementation
 * MacOS X has some difficulties, e.g. distinguishing sockets and pipes.
 * the OpenSSL tests require OpenSSL support by socat, must have openssl in
   $PATH, and "openssl s_server ..." needs enough entropy to generate a key.


Q: When I specify a dual address (two partial addresses linked with "!!") on
the command line, I get some message "event not found", and my shell history
has the line truncated. Not even protecting the '!'s with '\' helps.

A: '!' is appearently used by your shell as history expansion character. Say
"set +H" and add this line to your (bash) profile.


Q: On Solaris, socat was built successfully, but when started, it gets killed
with something like "ld.so.1: ./socat: fatal: libreadline.so.4: open failed: no
such file or directory"

A: The configure script finds your libreadline, but the runtime loader
doesn't. Add the directory where the library resides to your LD_LIBRARY_PATH
variable, e.g.: 
   LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/opt/sfw/lib/
   make distclean; ./configure; make


Q: On Solaris, socat was built successfully, but when started, an assertion
fails: "xioinitialize.c:25: failed assertion `3 << opt_crdly.arg3 == CRDLY'

A: Probably, in a second attempt you set the correct LD_LIBARY_PATH for socat,
but it had not been set during the ./configure run, or you did not "make clean"
before running configure. Try it again:
   make distclean; ./configure; make


Q: A socat process, run in background from an interactive shell, is always
stopped with all its child processes after about 5 minutes. killall -9 socat is
required to clean the system and allow socat to be started again.

A: The terminal (window) might have the TOSTOP flag set and one of the socat
processes wants to write to the terminal. Clear this flag in your shell:
   stty -tostop
and start socat again.
Thanks to Philippe Teuwen for reporting this situation.