Is it possible to use ftp to transfer a file from pc1 to pc2 with fix source location on pc1 and fix loaction on pc2 where it is to be copied/overwritten using any shell script or C program?
can scp is used for same purpose? how can i use that command in C program?
one more thing how a socket program can help in my condition?

Yes (assuming there's a suitable network, and network services, between the two).
Yes. Like this:You could use a socket program to send the file. Don't do that, as there are dozens of standards you could use, and you're more likely to make it less secure by using a custom program (fewer users => more bugs; security through obscurity doesn't work).

How is authentication handled in this situation?

hi

scp authenticates by asking for the user2 password when you press enter to execute the command

to send a file from here to there, if here is pc1 & there is pc2

scp /path/to/file user@pc2:destination/path <enter>

you will be promted for user@pc2 password.

to get a file from there to here

scp user@pc2:source/path destination/path <enter>

so

scp silly.txt john@dadspc:.

will copy silly.txt from the pwd of the local pc and copy it in the home directory of john on the pc who's hostname is dadspc. dadspc can be replaced with the ip address. 192.168.1.3 etc.

scp john@dadspc:silly.txt .

will copy silly.txt from the home directory of john on dadspc and place it in the pwd directory of the local user. notice the period (.) this represents here (pwd) as in the folder/directory you are in when you issue the command.

all files are encrypted. sshd must be running on the remote machine for this to work.

hope this helps
regards
GT

Hi globeTrotter,
i did as you said but i am getting followinf error in both cases you given after entering password for there pc
scp: /root/ppp: Permission denied

i check files ppp permissions and it is like
-rw-r--r-- 1 root root 251 Oct 26 11:06 ppp

one more thing both pcs are running sshd i also check that on both pcs

does scp require login as root to execute it? i am doing as root also but fail to transfer file

Are you trying to copy the file to /root/ppp on the other machine?

Past the whole command you used here.

hi


check in your /etc/ssh/sshd_config file for the following

PermitRootLogin no

if it's uncommented, as it should be for security, this then means root can not log in. also check for the comment in the /etc/ssh/ssh_config file. on my system i had to remove it from the ssh_config file for things to work.

sshd_config - is for the server side

ssh_config - is for client side

as a rule don't do anything as root. if you have root priviiliges on the other machine. it's safer to make a copy of files into a user directory and change owner & group. then scp as user. also make shure the sshd service is running on the remote system. obviously if the server is not running it can't serve!.

regards
GT

PS

if you can ssh in as root, you should be able to scp as root!!! if you can ssh in as root and not scp, then it's probably a syntax error in your scp command. post the exact scp syntax if this is the case.

regards
GT