This appendix covers the following topics:
SOCKS is a package consisting of a proxy server, client programs (rftp and rtelnet), and a library (libsocks) for adapting other applications into new client programs.
The original SOCKS was written by David Koblas (firstname.lastname@example.org). The SOCKS protocol has changed over time. The client library shipped as of printing corresponds to SOCKS v4.2. Since the server and the clients must use the same SOCKS protocol, this library doesn't work with servers of previous releases; clients compiled with these libraries won't work with older servers.
|If your client is using UDP to transfer data, you can't use SOCKS. To see if your client uses UDP, search for the string "SOCK_DGRAM" in your source.|
You can omit this step; the only reason for calling SOCKSinit() directly is to associate a name with your SOCKS client (rather than the generic "SOCKSclient" default string).
-Dconnect=Rconnect -Dgetsockname=Rgetsockname \ -Dbind=Rbind -Daccept=Raccept -Dlisten=Rlisten \ -Drcmd=Rrcmd -Dselect=Rselect
If you're using a Makefile, add these options to the definition of macro CFLAGS.
These options replace calls to certain functions with versions that use the SOCKS server:
|Non-SOCKS function:||SOCKS function:|
If you're using a Makefile, simply add this information to the definition of the macro LDFLAGS.
For most programs, the above steps should be sufficient to SOCKSify the package. If the above doesn't work, you may need to look at things a little more closely. The next section describes how the SOCKS library expects to be used.
The SOCKS library covers only some of the socket functions, which must be called in a particular order:
|You must use TCP; SOCKS doesn't support UDP.|
Most client programs fit these assumptions very well and can be SOCKSified without changing the code at all using the steps described in "How to SOCKSify a client."
Some client programs use a bind() before each connect(). If the bind() is used to claim a specific port or a specific network interface, the current SOCKS library can't accommodate such use. Very often though, such a bind() call is there for no specific reason and may simply be deleted.