Combining UDP and TCP connections
I am trying to build a simple client -server app, where multiple client sends price quotes to a server and the server does some analysis on these numbers and spits it back out to all the clients every 5 seconds or so. Before I start, I want to make sure I am thinking about it correctly. I was thinking that I could have on each client a UDP connection and a TCP connection, the TCP connection would be used to send the quotes to the server. This way I have a live connection and confirmed packet reception from client to server.
The UDP would be used for when the server sends back out the quotes to all the clients, since the server is just sending out back certain ones (the best quotes that is) to all the clients. Does that seem like a reasonable design?
The only reason is because the server should be sending out it's information via datagrams because it wants to send the same message to all the clients. So in my point of view it looks like it would be more efficient to send out one datagram, broadcasted instead of going through each client and sending the same thing, especially when I'm trying to send an update every 5 seconds or so.
Similar Messages
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Hi:
I have a question. As we know, scanning TCP ports is a lot eaiser than UDP ports because active UDP ports don't respond and there are other reasons as well.
try{
Socket soc= new Scoket(address, portnumber);
catch(Throwable e){ System.out.println(e)}
look at the code above, it can only tell you active TCP ports for the Throwable e tells you nothing about UDP ports. An active UDP port doesn' respond to the connection call "soc". Therefore it will throw an exception(connection refused) after trying to connect an active UDP port. This exception is just like those of closed TCP ports.
What i am saying is that active UDP ports will be treated the same as closed TCP ports. They are hidden in closed TCP ports. How do i sift them out? Any solutions?I am basically trying to determine how many UDP and TCP ports on a machine are open. Open TCP ports are easy to see. But UDP ports are tricky. Can you please tell me more in detail using a datagram socket?
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BEFW11S4 UDP AND TCP PORT opening
How do i open UDP AND TCP ports specifically TCP ports: 80, 6667, 28910, 29900, 29920
UDP ports: 4321, 27900 Its for a networkable game i need to open these ports to play it.Ok But when i try disabling the numbers in the forwarding field i run out of spaces in the field to be able to disable them Is there an advanced firewall settings that i dont know about? I put in all of the range forwarding and put the range forwarding start for example 80 originally (TCP ports: 80, 6667, 28910, 29900, 29920
UDP ports: 4321, 27900) The ones i try to disable i run out of fields to disable them in the forwarding for example there are 10 slots for disabling and Im trying to disable them on two numbers 192.168.1.101. and 192.168.1.100 So i need to disable them for both ip numbers I got 10 fields to enter it into them and 10 x 2 is more than the numbers..... You get me?? and on top of that i dont know if what i did was enough Linksys doesnt want to help me without paying 30 dollars so im just thinking i should buy a new router....... i mean they charge 39 dollars for a new router and they want me to pay 39 dollars for tech support it just doesnt make any sense........ -
Hi,
I have a connection between a measurement roboter and LabVIEW. I transmit the data above an TCP connection (for example the coordinate plane of the sensor). I have different ports to transmit the data. Is it possible to save the transmitted data and the TCP number of the Port?
Attachments:
datasend.vi 20 KBHi,
Just use the:
>
Regards, Christian -
How can I open both UDP and TCP ports
Hi,
How can i open both tcp and UDP ports for an IP in Cisco ASA?
Regards
EjazAre you referring to port opening in Cisco ASA to permit certain traffic? I believe the following document should help.
http://www.cisco.com/en/US/docs/security/asa/asa82/configuration/guide/acl_overview.html
Adding a Standard Access List
hostname(config)# access-list access_list_name standard {deny | permit} {any | ip_address mask}
Example:
hostname(config)# access-list OSPF standard permit 192.168.1.0 255.255.255.0
http://www.cisco.com/en/US/docs/security/asa/asa82/configuration/guide/acl_standard.html
Adding an Extended Access List
access-list access_list_name [line line_number] [extended] {deny | permit} protocol source_address mask [operator port] dest_address mask [operator port | icmp_type] [inactive]
Example:
hostname(config)# access-list ACL_IN extended permit ip any any
http://www.cisco.com/en/US/docs/security/asa/asa82/configuration/guide/acl_extended.html
Hope this will help. -
Maximum # of UDP and TCP port Mappings
Does anyone know for sure the total number of port mappings you can create on the airport extreme?
ThanksOk But when i try disabling the numbers in the forwarding field i run out of spaces in the field to be able to disable them Is there an advanced firewall settings that i dont know about? I put in all of the range forwarding and put the range forwarding start for example 80 originally (TCP ports: 80, 6667, 28910, 29900, 29920
UDP ports: 4321, 27900) The ones i try to disable i run out of fields to disable them in the forwarding for example there are 10 slots for disabling and Im trying to disable them on two numbers 192.168.1.101. and 192.168.1.100 So i need to disable them for both ip numbers I got 10 fields to enter it into them and 10 x 2 is more than the numbers..... You get me?? and on top of that i dont know if what i did was enough Linksys doesnt want to help me without paying 30 dollars so im just thinking i should buy a new router....... i mean they charge 39 dollars for a new router and they want me to pay 39 dollars for tech support it just doesnt make any sense........ -
People told me that data might go lost if I use UDP Protocol, so I have to use TCP.
But I am quite confused cause I read that the data link layer will make sure the data transfers correctly, so I suppose no data would be lost even if I use UDP cause it's based on the link layer.
Can someone solve my puzzle?But the data link already take care of this. So no
packets should be lost.No. -
^^^ Just need help with that, its for my PS3, i called Sony after getting DNS errors(80710102) and they told me i need to enter the numbers they gave me, i just want to know were to pit them... And my router is a WRT54G btw...
Message Edited by Gran_Turismo on 06-28-2007 10:39 PMfrom the computer wired to the router , access the web interface of the router using http://192.168.1.1 .. the default password is "admin"...once on the ui go to the "applications and gaming" tab and click on the "port trigerring" subtab .. enter the port numbers on this page ..
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Hey everyone,
I'm behind a firewall that blocks all UDP (torrents, games...) requests.
I usually ssh to my server and forward all the trafic to it using a transparent
proxy application (sshuttle). I saw that openvpn handles UDP as well (sshuttle doesn't).
I read the documentation of openvpn but I didn't understand which flags to use
and which not to. Actually I suck at networking and I'm not even sure if the title of the question
is correct (would explain why I couldn't find anything on the forum/online).
So could you please help me out? and sorry for any mistake I did.
ThanksOpenVPN, has two operating mode: tun and tap. Tun just tunnels IP traffic (UDP and TCP), while Tap acts like a real ethernet cable. To achieve this, OpenVPN has to make a network connection with the remote server. To do so, you have two choices again: UDP and TCP.
What you want is probably tun+tcp, which will make the UDP traffic going into OpenVPN to be transmitted over the TCP connection and go out of the server as UDP.
The config options are
proto tcp
dev tap
The wiki entry (https://wiki.archlinux.org/index.php/Op … ll_OpenVPN) should work fine for you. Just don't forget to use "proto tcp" in both server and client configs. The default setup should be perfectly fine for you.
As noted by brain0, tunelling UDP over TCP will cause higher latency on UDP. It should work fine for torrents, but the latency will be something 1.5x the latency from you and the server + the latency between the server and the final destination of the UDP traffic. Gaming on that might be painful. -
Is something intercepting my TCP connections?
I have BT Infinite and have been testing my network latency using Ping for ICMP RTT, and NPing to measure TCP SYN/ACK RTT and UDP RTT.
I have found that my TCP connect latency, i.e. time create a TCP connection to a remote host, is always about 10ms, even when the ping is much higher. For example my ICMP ping to the time server 0.uk.pool.ntp.org (192.238.80.20) is about 160ms, but my TCP ping is about 10ms. I get the same result for almost any server on the internet anywhere in the world on any port, the TCP ping varies between 3ms and 12ms.
This implies that something local to my internet connection is intercepting my TCP connections, responding to my TCP connection requests and forwarding on the request to the remote host, e.g. a TCP proxy server, or firewall. The ping and TCP connection time to my broadband router is 1ms or under so its not my equipment. So I assume BT have some device on my connection path.
Has anyone experienced similar issues or knows what is causing this? Is it Parental Control network filters - I thought these worked by blocking DNS requests not by proxying and filtering traffic?I have BT Infinite and have been testing my network latency using Ping for ICMP RTT, and NPing to measure TCP SYN/ACK RTT and UDP RTT.
I have found that my TCP connect latency, i.e. time create a TCP connection to a remote host, is always about 10ms, even when the ping is much higher. For example my ICMP ping to the time server 0.uk.pool.ntp.org (192.238.80.20) is about 160ms, but my TCP ping is about 10ms. I get the same result for almost any server on the internet anywhere in the world on any port, the TCP ping varies between 3ms and 12ms.
This implies that something local to my internet connection is intercepting my TCP connections, responding to my TCP connection requests and forwarding on the request to the remote host, e.g. a TCP proxy server, or firewall. The ping and TCP connection time to my broadband router is 1ms or under so its not my equipment. So I assume BT have some device on my connection path.
Has anyone experienced similar issues or knows what is causing this? Is it Parental Control network filters - I thought these worked by blocking DNS requests not by proxying and filtering traffic? -
UDP vs TCP (hands-on experience required)
Dearest colleagues,
I've done a few hours of research learning what I can about TCP vs UDP. I could still use some input from those of you who have used both in real-world, scaleable, distributed, commercial, and successful projects.
I have a new position at a new company. My part of this project consists of 3 types of distributed Java server programs: desktop client, data server, and controller server. Thousands of desktop clients will be periodically transferring "megs" of data to several data servers. The (singular) controller will persist metadata into a database, and also coordinate data transfer between the desktop clients and the data servers.
TCP seems appropriate for all "control" and metadata communications between all these components. Everyone talks to the controller for everything, except for the periodic transfer of the "actual" data. The desktop clients send that data directly to the appropriate data server using either UDP or TCP.
One key project requirement is the ability to provide network throttling control, so as not to saturate the client's LAN or WAN. This product mustn't disrupt the client's real-time network data (like VoiP and video conferencing). I expect the controller server to manage this.
Someone with more seniority than me at this company has suggested TFTP (which uses UDP) as the best protocol for the data transfer protocol. This person also claims that UDP allows larger packet sizes and less protocol overhead, resulting in greater data transfer rates than TCP.
I have a number of concerns and questions:
1) Can't the packet sizes be set for both UDP and TCP? If so, can't one equal both (in terms of average overhead) just by adjusting the packet sizes?
2) I realize that one needs to accomodate UDP droppage in order to compare throughput with TCP. In a LAN environment is it reasonable to assume that droppage would be minimal or zero? )Otherwise wouldn't it be a LAN problem someone would be fixing?)
3) If #2 above allows me to assume minimal UDP droppage, does the underlying packet protocol overhead difference give UDP a substantial throughput advantage? If so, how much (roughly)?
4) I believe UDP packets are treated as "high priority" but "low reliability". For my application, doesn't that mean that UDP is more likely to cause problems by competing for VoiP and VidCon bandwith?
5) What about trying to write my servers to allow for either UDP or TCP to be
used for data transfer? If you have done this, would you recommend for or against it? Why?
6) If you had to recommend just one book for me for right now (given this project), which would it be:
6a) Java Distributed Computing (O'Reilly) by Jim Farley
6b) Internetworking with TCP/IP by Doug Comer's
6c) Unix Network Programming by Richard Stevens
Being the New Kid on the Block at this company, I need to know all I can as I navigate the politics with this more senior person. I'm no newbie - I've been programming professionally for 27 years, the last 6 in Java including networking, sockets, JDBC, etc.
Thank you very much for your assistance.Dearest colleagues,
I've done a few hours of research learning what I can
about TCP vs UDP. I could still use some input from
those of you who have used both in real-world,
scaleable, distributed, commercial, and successful
projects.
I have a new position at a new company. My part of
this project consists of 3 types of distributed Java
server programs: desktop client, data server, and
controller server. Thousands of desktop clients will
be periodically transferring "megs" of data to
several data servers. The (singular) controller will
persist metadata into a database, and also coordinate
data transfer between the desktop clients and the
data servers.
TCP seems appropriate for all "control" and metadata
communications between all these components.
Everyone talks to the controller for everything,
, except for the periodic transfer of the "actual"
data. The desktop clients send that data directly to
the appropriate data server using either UDP or TCP.Key feature of TCP is connection orianted and reliablity. If you need long sessions with high reliability TCP is the way to go.
(Long sessions means the client do multiple transaction through same session)
But reliablity of TCP comes at a cost. (Less bandwith efficiency) but of course if you need to transfer data I say TCP is better.
But if you want your clients need to work in unreliable network links (Onse that breakes down often) TCP might cause problems since you have to re establish the connection every time there is a problem.
Also if the sessions are short then UDP is better becouse if you Use TCP for very short sessions Connection establishment and closing can take more time that the actual data transfer.
But if you use UDP you must deal with the unreliability.
One key project requirement is the ability to provide
network throttling control, so as not to saturate the
client's LAN or WAN. This product mustn't disrupt
the client's real-time network data (like VoiP and
video conferencing). I expect the controller server
to manage this.It is true that TCP add more owerhead than UDP but in most cases compaired to the amount of data you transfer through network that is nothing.
Key to save the bandwith is to designe a efficint communication protocol which minimize the amount of data that you have to transfer.
Also you can Implement input/output streams which can limit the number of bytes that can be written or read through them. (Even though that got nothing to do with networking that will give you full control over the bandwidth usage by the programs)
Someone with more seniority than me at this company
has suggested TFTP (which uses UDP) as the best
protocol for the data transfer protocol. This person
also claims that UDP allows larger packet sizes and
less protocol overhead, resulting in greater data
transfer rates than TCP.TFTP is good for transfering small files through networrks since there is less overhead but when it comes to large amounts of data there is no much difference.
But TFTP have a advantage over ureliable networks.
(If the networks fails TCP connection fails, but in UDP a network faliour is just a loss of several datagrams which the programs anyways should be able to handle)
I have a number of concerns and questions:
1) Can't the packet sizes be set for both UDP and
TCP? If so, can't one equal both (in terms of
average overhead) just by adjusting the packet
sizes?In tcp packet size is not a big issue since data are transfered through stream. Once the streams are open you can keep them opena as long as you want and send as many bytes as you want.
2) I realize that one needs to accomodate UDP
droppage in order to compare throughput with TCP. In
a LAN environment is it reasonable to assume that
droppage would be minimal or zero? )Otherwise
wouldn't it be a LAN problem someone would be
fixing?)Even though UPD is said to be unreliable if the programs are written well. In a LAN UDP is almost as areliable as TCP(This is depend on the reliability of LAN)
Thats why it says when you write UDP applications you must test them in slow unreliable Wan links.
3) If #2 above allows me to assume minimal UDP
droppage, does the underlying packet protocol
overhead difference give UDP a substantial throughput
advantage? If so, how much (roughly)?It depends
Ex:-
Lts assume UDB header is 25 bytes and TCP heade is 50 for simplicity
If your data size is 10 byte.
lets say UDP adds overhead of 5 bytes
now the efficiency is 10/(10+25) = 0.38
If TCP adds 10 overhead bytes
now the efficiency is 10/(10+50) = 0.16
lets doa the same calculation for 1000 bytes
UDP
1000/(1000 + 25) = 0.97
TCP
1000/(1000+ 50) = 0.95
So it depends on your application and data volume
4) I believe UDP packets are treated as "high
priority" but "low reliability". For my application,
doesn't that mean that UDP is more likely to cause
problems by competing for VoiP and VidCon bandwith?No Priority is set on IP level so it can be applied to both TCP and UDP
5) What about trying to write my servers to allow
for either UDP or TCP to be
used for data transfer? If you have done this, would
you recommend for or against it? Why?For data transfer I recomend TCP becouse reliability is important.
If you use UDP you have to handle reliability (Lots of programming)
6) If you had to recommend just one book for me for
right now (given this project), which would it be:
6a) Java Distributed Computing (O'Reilly) by Jim
Farley
6b) Internetworking with TCP/IP by Doug Comer's
6c) Unix Network Programming by Richard Stevens
Being the New Kid on the Block at this company, I
need to know all I can as I navigate the politics
with this more senior person. I'm no newbie - I've
been programming professionally for 27 years, the
last 6 in Java including networking, sockets, JDBC,
etc.
Thank you very much for your assistance. -
Solaris Kernel and TCP/IP Tuning Parameters (Continued)
This page describes some configuration optimizations for Solaris hosts running ATG Page Serving instances (application servers) that will increase server efficiency.
Note that these changes are specific to Solaris systems running ATG application servers (+page serving+ instances). Do not use these on a web server or database server. Those systems require entirely different settings.
h3. Solaris 10 Kernel
Adjust /etc/system (parameters below) and reboot the system.
set rlim_fd_cur=4096
set rlim_fd_max=4096
set tcp:tcp_conn_hash_size=32768
set shmsys:shminfo_shmmax=4294967295
set autoup=900
set tune_t_fsflushr=1h4. Set limits on file descriptors
{color:blue}set rlim_fd_max = 4096{color}
{color:blue}set rlim_fd_cur = 4096{color}
Raise the file-descriptor limits to a maximum of 4096. Note that this tuning option was not mentioned in the "Sun Performance And Tuning" book.
[http://download.oracle.com/docs/cd/E19082-01/819-2724/chapter2-32/index.html]
h4. Increase the connection hash table size
{color:blue}set tcp:tcp_conn_hash_size=8192{color}
Increase the connection hash table size to make look-up's more efficient. The connection hash table size can be set only once, at boot time.
[http://download.oracle.com/docs/cd/E19455-01/816-0607/chapter4-63/index.html]
h4. Increase maximum shared memory segment size
{color:blue}set shmsys:shminfo_shmmax=4294967295{color}
Increase the maximum size of a system V shared memory segment that can be created from roughly 8MB to 4GB.
This provides an adequate ceiling; it does not imply that shared memory segments of this size will be created.
[http://download.oracle.com/docs/cd/E19683-01/816-7137/chapter2-74/index.html]
h4. Increase memory allocated for dirty pages
{color:blue}set autoup=900{color}
Increase the amount of memory examined for dirty pages in each invocation and frequency of file system synchronizing operations.
The value of autoup is also used to control whether a buffer is written out from the free list. Buffers marked with the B_DELWRI flag (which identifies file content pages that have changed) are written out whenever the buffer has been on the list for longer than autoup seconds. Increasing the value of autoup keeps the buffers in memory for a longer time.
[http://download.oracle.com/docs/cd/E19082-01/819-2724/chapter2-16/index.html]
h4. Specify the time between fsflush invocations
Specifies the number of seconds between fsflush invocations.
{color:blue}set tune_t_fsflushr=1{color}
[http://download.oracle.com/docs/cd/E19082-01/819-2724/chapter2-105/index.html]
Again, note that after adjusting any of the preceding kernel parameters you will need to reboot the Solaris server.
h3. TCP
ndd -set /dev/tcp tcp_time_wait_interval 60000
ndd -set /dev/tcp tcp_conn_req_max_q 16384
ndd -set /dev/tcp tcp_conn_req_max_q0 16384
ndd -set /dev/tcp tcp_ip_abort_interval 60000
ndd -set /dev/tcp tcp_keepalive_interval 7200000
ndd -set /dev/tcp tcp_rexmit_interval_initial 4000
ndd -set /dev/tcp tcp_rexmit_interval_max 10000
ndd -set /dev/tcp tcp_rexmit_interval_min 3000
ndd -set /dev/tcp tcp_smallest_anon_port 32768
ndd -set /dev/tcp tcp_xmit_hiwat 131072
ndd -set /dev/tcp tcp_recv_hiwat 131072
ndd -set /dev/tcp tcp_naglim_def 1h4. Tuning the Time Wait Interval and TCP Connection Hash Table Size
{color:blue}/usr/sbin/ndd -set /dev/tcp tcp_time_wait_interval 60000{color}
The tcp_time_wait_interval is how long a connection stays in the TIME_WAIT state after it has been closed (default value 240000 ms or 4 minutes). With the default setting, this socket will remain for 4 minutes after you have closed the FTP connection. This is normal operating behavior. It is done to ensure that any slow packets on the network will arrive before the socket is completely shutdown. As a result, a future program that uses the same socket number won't get confused upon receipt of packets that were intended for the previous program.
On a busy Web server a large backlog of connections waiting to close could build up and the kernel can become inefficient in locating an available TCP data structure. Therefore it is recommended to change this value to 60000 ms or 1 minute.
h4. Tuning the maximum number of requests per IP address per port
{color:blue}ndd -set /dev/tcp tcp_conn_req_max_q 16384{color}
{color:blue}ndd -set /dev/tcp tcp_conn_req_max_q0 16384{color}
The {color:blue}tcp_conn_req_max_q{color} and {color:blue}tcp_conn_req_max_q0{color} parameters are associated with the maximum number of requests that can be accepted per IP address per port. tcp_conn_req_max_q is the maximum number of incoming connections that can be accepted on a port. tcp_conn_req_max_q0 is the maximum number of “half-open” TCP connections that can exist for a port. The parameters are separated in order to allow the administrator to have a mechanism to block SYN segment denial of service attacks on Solaris.
The default values are be too low for a non-trivial web server, messaging server or directory server installation or any server that expects more than 128 concurrent accepts or 4096 concurrent half-opens. Since the ATG application servers are behind a DMZ firewall, we needn't starve these values to ensure against DOS attack.
h4. Tuning the total retransmission timeout value
{color:blue}ndd -set /dev/tcp tcp_ip_abort_interval 60000{color}
{color:blue}tcp_ip_abort_interval{color} specifies the default total retransmission timeout value for a TCP connection. For a given TCP connection, if TCP has been retransmitting for tcp_ip_abort_interval period of time and it has not received any acknowledgment from the other endpoint during this period, TCP closes this connection.
h4. Tuning the Keep Alive interval value
{color:blue}ndd -set /dev/tcp tcp_keepalive_interval 7200000{color}
{color:blue}tcp_keepalive_interval{color} sets a probe interval that is first sent out after a TCP connection is idle on a system-wide basis.
If SO_KEEPALIVE is enabled for a socket, the first keep-alive probe is sent out after a TCP connection is idle for two hours, the default value of the {color:blue}tcp_keepalive_interval{color} parameter. If the peer does not respond to the probe after eight minutes, the TCP connection is aborted.
The {color:blue}tcp_rexmit_interval_*{color} values set the initial, minimum, and maximum retransmission timeout (RTO) values for a TCP connections, in milliseconds.
h4. Tuning the TCP Window Size
{color:blue}/usr/sbin/ndd -set /dev/tcp tcp_xmit_hiwat 65535{color}
{color:blue}/usr/sbin/ndd -set /dev/tcp tcp_recv_hiwat 65535{color}
Setting these two parameters controls the transmit buffer and receive window. We are tuning the kernel to set each window to 65535 bytes. If you set it to 65536 bytes (64K bytes) or more with Solaris 2.6, you trigger the TCP window scale option (RFC1323).
h4. Tuning TCP Slow Start
{color:blue}/usr/sinb/ndd -set /dev/tcp tcp_slow_start_initial 4{color}
tcp_slow_start_initial is the number of packets initially sent until acknowledgment, the congestion window limit.
h4. Tuning the default bytes to buffer
{color:blue}ndd -set /dev/tcp tcp_naglim_def 1{color}
{color:blue}tcp_naglim_def{color} is the default number of bytes to buffer. Each connection has its own copy of this value, which is set to the minimum of the MSS for the connection and the default value. When the application sets the TCP_NODELAY socket option, it changes the connection's copy of this value to 1. The idea behind this algorithm is to reduce the number of small packets transmitted across the wire by introducing a short (100ms) delay for packets smaller than some minimum.
Changing the value of tcp_naglim_def to 1 will have the same effect (on connections established after the change) as if each application set the TCP_NODELAY option.
{note}
The current value of any of the TCP parameters can be displayed with the command ndd get. So to retrieve the current setting of the {color:blue}tcp_naglim_def parameter{color}, simply execute the command:\\
{color:blue}ndd -get /dev/tcp tcp_naglim_def{color}
{note}
h3. References
Solaris Tunable Parameters Reference Manual
[http://download.oracle.com/docs/cd/E19455-01/816-0607/index.html]
WebLogic Server Performance and Tuning
[http://download.oracle.com/docs/cd/E11035_01/wls100/perform/OSTuning.html]For example,
Socket.setSoTimeout() sets SO_TIMEOUT option and I
want to what TCP parameter this option corresponds in
the underlying TCP connection.This doesn't correspond to anything in the connection, it is an attribute of the API.
The same questions
arises fro other options from SocketOptions class.setTcpNoDelay() controls the Nagle algorithm. set{Send,Receive}BufferSize() controls the local socket buffers.
Most of this is quite adequately described in the javadoc actually. -
ASA 5505:Static Routing and Deny TCP connection because of bad flag
Hi Everybody,
I have a problem. I made a VPN site-2-site with 2 ASA 5505. The VPN works great. And I create a redondant link if the VPN failed.
In fact, I use Dual ISP with route tracking. If the VPN fails, the default route change to an ISDN router, situated on the inside interface.
When I simulated a VPN fail, the ASAs routes switch automatically on backup ISDN routers. If I ping elements, it works great. But when i try TCP connection like telnet, the ASAs deny connections:
%PIX|ASA-6-106015: Deny TCP (no connection) from 172.16.10.57/35066 to 172.16.18.1/23 flags tcp_flags on interface interface_name.
the security appliance discarded a TCP packet that has no associated connection in the security appliance connection table. The security appliance looks for a SYN flag in the packet, which indicates a request to establish a new connection. If the SYN flag is not set, and there is not an existing connection, the security appliance discards the packet.
thanks!
EDIT: On the schema, The interface of the main asa is 172.16.18.148...Check if the xlate timer is set greater than or equal to what the conn timer, so as not to have connections waiting on xlates that no longer exist. To minimize the number of attempts, enable "service resetinbound" . The PIX will reset the connection and make it go away. Without service resetinbound, the PIX Firewall drops packets that are denied and generates a syslog message stating that the SYN was a denied connection.
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Opening and closing Multiple TCP connections issues
Hi all I am having an issue with the TCP VI’s and wondering if anyone has experienced this issue.
My application is required to scan 50-100 IP addresses (statically assigned) and discover if an Ethernet device is connect at that IP address. Currently I am able to achieve this by opening a TCP connection and testing the error cluster to determine if a timeout has occurred (no timeout error means Ethernet device available at the IP address). I then ensure that the TCP connections are closed.
The issue I am have is that I require a 1 second delay between the TCP open and the TCP close which significantly slows down the process. Without the 1 second delay the vi successfully connects to the device once then fails to make any TCP connect regardless of the time delay until the PC is reset.
If anyone has any advice I would be very grateful
David Barr
P.S. I have attached a simplified section of code showing this issue
Attachments:
TCP Open close issue.vi 15 KBsmercurio_fc wrote:
If I understand you correctly you want the time delay to be 1 second if there's a successful connection....
While I don't have a specific answer for this problem. I want to clarify for him. I believe the issue is, what if all connections ARE there? That means you keep returning a wait of 1 second 50-100 times so It takes 50-100 seconds just to initialize. I think the user is looking for a way to check for valid connections, but do so in such a way that eliminates the need for a wait which is greatly slowing things down.
CLA, LabVIEW Versions 2010-2013 -
TCP connection in labview and C program
Hi there,
I have a server program written in C and running under linux, it
accept connection from client and send series of data to client
through TCP socket. I was using the "simple data client.vi" as the
client.
I tried to send integer number 1, 2,3.. , but the client failed to
correctly decode the data since it read everything as string. I was
wondering if there is a solution to read binary data in labview TCP
connection? I really don't want to encode the double into string and
send it to client through TCP socket in my server program, since it's
not efficient.
thanks !> I have a server program written in C and running under linux, it
> accept connection from client and send series of data to client
> through TCP socket. I was using the "simple data client.vi" as the
> client.
> I tried to send integer number 1, 2,3.. , but the client failed to
> correctly decode the data since it read everything as string. I was
> wondering if there is a solution to read binary data in labview TCP
> connection? I really don't want to encode the double into string and
> send it to client through TCP socket in my server program, since it's
> not efficient.
> thanks !
>
The string is often used in LV as a general buffer. Type Cast the
string as the appropriate integer and it should be fine. If the integer
has been transmitted in litt
le endian byte order, you will need to use
the Advanced byte and word swapping functions in LV in order to reorder
the integer contents -- LV always assumes big-endian binary format.
Greg McKaskle
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