Visit Our UNIX and Linux User Community

close existing tcp connection in C

Thread Tools Search this Thread
Top Forums Programming close existing tcp connection in C
# 1  
Old 01-19-2009
close existing tcp connection in C

Hello. I would like to know how to close an existing tcp socket. I have read some stuff and learned how to create a socket and then close it but have not found anything about how to close an existing tcp socket created by another application. The situation is this: I have an ODBC server running and sometimes it hangs and needs to be reset. The problem is when people still have the client application (Crystal Reports) open, The ODBC server will not restart because the socket it still open, but in a FIN_WAIT state. I have looked at tcpkill.c from dsniff-2.3, but I really do not know what I am looking at. I do not have much C knowledge. Can anyone help me? Thanks
# 2  
Old 01-20-2009


What exactly do you want to know?. tcpkill.c use libpcap to filter some packages directed to the socket that you want to close.

You have to compile tcpkill.c and run it up as a root user in order to close the socket.
# 3  
Old 01-21-2009
Thanks for the reply. I understand that, it's just that tcpkill will terminate all connections, and that is certainly not what I want to do. I would like to kill any sockets using a specific port.
# 4  
Old 01-21-2009
Hi raidzero,

I'm analyzing the tcpkill.c source code and I will try to make some changes to reset only a specific tcp connection. I will let you know if it works as soon as possible.

# 5  
Old 01-21-2009
wow! than you so much that's awesome
# 6  
Old 01-21-2009
What OS are you using? Some OSes come with the ndd utility which can be used to close a FIN_WAIT'ed socket.
# 7  
Old 01-21-2009
It will be used on AIX 5.3.

Previous Thread | Next Thread
Test Your Knowledge in Computers #654
Difficulty: Easy
DOS was initially released on the IBM System/360.
True or False?

10 More Discussions You Might Find Interesting

1. UNIX for Advanced & Expert Users

30 tcp connections Established for a while and after a few minutes are close

Good morning, I need your help please After Restarting Aps or connection, these are connections tcp 0 0 ESTABLISHED tcp 0 47 ESTABLISHED tcp 0 0 ... (4 Replies)
Discussion started by: alexcol
4 Replies

2. Shell Programming and Scripting

[Solved] Rsh does not close connection on exit

Dear all, We have a service that we start up remotely with rsh but unfortunately, the rsh never returns to the calling server. This seems to be because the processes of the service we've just started hold the port open.RBATTE1 @ /home/RBATTE1>netstat -na|grep 49.51 tcp4 0 0 ... (1 Reply)
Discussion started by: rbatte1
1 Replies

3. UNIX for Dummies Questions & Answers

Remotely close & rerun SSH connection

I'm trying to remotely run an upgrade script (via SSH) that update the SSH script on several hosts, just need to add several flags for the ssh command to look like this: ssh -Nf -i id_logs -o ExitOnForwardFailure=yes -o StrictHostKeyChecking=no -o ServerAliveInterval=60 -o ServerAliveCountMax=5... (4 Replies)
Discussion started by: OdedOvdat
4 Replies

4. Solaris

Ssh to Solaris 10 server - close connection

Can ssh to server. Asks for password. Then seems to time out and close the connection. Any ideas? ---------- Post updated at 09:30 AM ---------- Previous update was at 07:51 AM ---------- Here is output from ssh -vvv -l user <IPaddress> debug3: packet_send2: adding 64 (len 59 padlen 5... (4 Replies)
Discussion started by: psychocandy
4 Replies

5. Solaris

many tcp connection in close-wait

Hi, I use solaris Unix . I find there is some problem in application and it generate many "close-wait" tcp connect and stay in the server . it is generate by process id 7740 root@XX # netstat -an | grep CLOSE_WAIT | wc -l 285 root@XX # netstat -an | grep CLOSE_WAIT ... (2 Replies)
Discussion started by: abcdef
2 Replies

6. Programming

TCP trashing data on application close

I am using c to send data to a socket with the following commands: socket = socket(AF_INET, SOCK_STREAM, ptrp->p_proto); ioctl(socket, FIONBIO, (char *)&on); connect(socket) send(socket,data) shutdown(socket, SHUT_WR); recv(socket) //ready last of data waiting on the port //note this is... (3 Replies)
Discussion started by: metrix
3 Replies

7. Shell Programming and Scripting

Usage of NOHUP - How to keep the child process running even if I close the Server connection

Hi. ! When I use the 'NOHUP' along with the '&', the process will be running in the background. Even when I attempt to close (Meaning 'EXIT') the session (say PUTTY in this case), it wont exit unless the process is completed. But, say when I forcefully terminate the session (SHUT DOWN the... (2 Replies)
Discussion started by: WinBarani
2 Replies

8. Shell Programming and Scripting

How to close TELNET Connection

Hi, I have logged into a system using Telnet and iam unable to close the connection to connect to the next system using arrays. Iam getting error "Connection Timed Out" Iam using net::Telnet module. Please suggest.. (1 Reply)
Discussion started by: sudhakaryadav
1 Replies

9. UNIX for Dummies Questions & Answers

close tcp port

Hello, I have a service running (ODBC) and every now and then it will hang and I will have to stop and restart the service. The problem is when I stop the service, it indeed stops the service, but netstat reports a tcp port still open with the fin_wait_2 status. Then I must close the client... (1 Reply)
Discussion started by: raidzero
1 Replies

10. UNIX for Dummies Questions & Answers

ftp - Connection close

Hi Can someone help me what is the problem, when i try to login via ftp, though i entered the correct password, i got an error message Connection refused. please help. thanks (3 Replies)
Discussion started by: kaibiganmi
3 Replies

Featured Tech Videos