can-not detect TCP disconnects well Post: 302319463

Sponsored Content

Top Forums Programming can-not detect TCP disconnects well Post 302319463 by ogerassimov on Monday 25th of May 2009 10:00:47 AM

05-25-2009

Registered User

Change Protocol

Hello pjwhite,

It the remote computer simply crash or network is cut, then how to to catch that situation? As I understand that's the question?

Let me say few words about TCP/IP

1. It is reliable and stream based protocol ...

Each sending side has a buffer for example 32 kb buffer and if there is room at the buffer all "send" or "write" operations succeeds immediately without any error and without caring if the data reaches the remote end or not. Next the tcp/ip implementation starts to send the current window of the stream as a sequence of IP packets re-transmitting them until any reply from the remote side. Without any reply this side will not know what happen.

I would like to propose to you to change your protocol ( if yours ), and to introduce ability to ping the other side with a special kind of message. Most already designed protocol has ability to do such activity or they don't need it.

I've seen from your post that you have already created that.
I mean you can create a special message that requires a special reply :

1. If there is some in-activity time you can simply pass the special message, just 1, and if the reply didn't come to start re-establishing the connection.

2. 2 is like 1.but uses OOB ( Out-Of-Band Data for such "ping" message )

Actually after sending the special message if there is no reply you can try to re-connect and if that operation fails. Actually reconnecting will also "hang" if the network is down. So timeout and asynchronoust connect is also recommended.

Best Regards
O.

or try the mika's recommendation to use keep alive but please check it if it is working. And you should configure something

"A Transmission Control Protocol (TCP) keep-alive packet is an acknowledgment (ACK) with the sequence number set to one less than the current sequence number for the connection. The Transmission Control Protocol/Internet Protocol (TCP/IP) stack can automatically generate these keep-alive messages to verify that the computer at the remote end of a connection is still available."

Best Regards
O.

ogerassimov

View Public Profile for ogerassimov

Find all posts by ogerassimov

10 More Discussions You Might Find Interesting

1. AIX

aix telnet disconnects

We're having problems getting disconnected from AIX with our telnet sessions. I can't ping the server when this happens, either. Other serves can be pinged at the same time. This happens both at unix and within the database. Database locks remain when editing files. unix logins remain after...

2. AIX

Telnet disconnects on handheld device AIX

I have intermec handheld device which is connecting to AIX Server on port 12431 or whatever. ( oracle application ) The handheld device connects for few seconds and then disconnects from the AIX server. Once it disconnects the handheld device automatically switches off. Are there any...

3. Windows & DOS: Issues & Discussions

Putty disconnects after sometime

i am using Putty to do ssh to all the unix nodes that we have in our work environment. it is very strange that all my network connections will timeout quickly in 10 mins, it can either be a putty connection, sqlplus or toad. is there some setting that can help to prevent this. please let me know...

4. Programming

How detect TCP/IP socket shutdown when ethernet cable is disconnected

Hi, I want to code TCP/IP client/server in linux application capable to fastly detect ethernet cable disconnection in any condition. So I have activate SO_KEEPALIVE options and set TCP_KEEPCNT, TCP_KEEPIDLE and TCP_KEEPINTVL to 1. When I disconnect ethernet cable I have the following...

5. Programming

Socket endpoints disconnects

Hello, I am able to establish a connection, and transfer data. Occasionally the receiving client will block in read(2) and stay that way until it is killed. initial: server: netstat -aveeopT tcp 0 0 *:17398 *:* LISTEN server-user...

6. Programming

[C++] [Unix] TCP non-blocking. Detect server disconnection procedure over, from client.

Hello! I searched forum for similar topic, with no luck, if you know one, delete this topic, and send me private message with link please. Little background: I have a lot of clients and one serwer. Client can make multiple connections on different ports and ips, but only one can be acctive...

7. Red Hat

Network disconnects often

Hi , My redhat 5 frequently disconnects from network. Once rebooted , network is working for one day or two. After that the NIC suddently stops working. Even if i give "#service network restart" or ifup eth0 commands it won't come up. I even tried reconfigure the network card. but no use. Only...

8. Solaris

Too much TCP retransmitted and TCP duplicate on server Oracle Solaris 10

I have problem with oracle solaris 10 running on oracle sparc T4-2 server. Os information: 5.10 Generic_150400-03 sun4v sparc sun4v Output from tcpstat.d script TCP bytes: out outRetrans in inDup inUnorder 6833763 7300 98884 0...

9. UNIX for Dummies Questions & Answers

Persistent terminal windows across viewer disconnects

Is there a way to have persistent terminal windows to redhat server across viewer disconnects? I can do that with the help of an extra MS Windows server and rdp, but is there a way of doing that without the Windows server? Here's the scenario. I have multiple redhat servers (VMs) which have no...

10. SCO

Telnet session disconnects abruptly

I have inherited and SCO OpenServer Release 6 server. The clients connect using telnet to get to a proprietary database application for Service tickets. The issue I am currently having is that the connection just stops abruptly and you can see "telnet session terminated" on the terminal emulation...

LEARN ABOUT OSF1

icmp

icmp(7) 						 Miscellaneous Information Manual						   icmp(7)

NAME

       icmp - Internet Control Message Protocol

SYNOPSIS

       #include <sys/socket.h> #include <netinet/in.h>

       The following is the socket call for sockets using the IPv4 address format:

       s = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);

       The following is the socket call for sockets using the IPv6 address format: s = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);

DESCRIPTION

       The  Internet Control Message Protocol (ICMP) is the error and control message protocol used by the Internet Protocol (IP) and the Internet
       Protocol family.  It may be accessed through a raw socket for network monitoring and diagnostic functions.  ICMP  sockets  are  connection-
       less, and are normally used with the sendto() and recvfrom() functions.	The connect() function may also be used to fix the destination for
       future packets, in which case the read() or recv() and write() or send() functions may be used.

       Outgoing packets automatically have an IP header prepended to them (based on the destination address).  Incoming packets are received  with
       the IP header and options intact.

ERRORS

       If a socket operation fails, errno may be set to one of the following values: The socket is already connected.  This error occurs when try-
       ing to establish connection on a socket or when trying to send a datagram with the destination address specified.  The destination  address
       of  a  datagram was not specified, and the socket has not been connected.  The system ran out of memory for an internal data structure.	An
       attempt was made to create a socket with a network address for which no network interface exists.

RELATED INFORMATION

       Functions: send(2), recv(2)

       Files: netintro(7), inet(7), ip(7)

       RFC 792, "Internet Control Message Protocol"

       RFC 2463, "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6)" delim off

																	   icmp(7)

10 More Discussions You Might Find Interesting

1. AIX

aix telnet disconnects

Discussion started by: e1lyons

2. AIX

Telnet disconnects on handheld device AIX

Discussion started by: filosophizer

3. Windows & DOS: Issues & Discussions

Putty disconnects after sometime

Discussion started by: sudhiroracle

4. Programming

How detect TCP/IP socket shutdown when ethernet cable is disconnected

Discussion started by: jeje_clb