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TCP/IP

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Transmission Control Protocol/Internet Protocol (TCP/IP) is the set of networking protocols that define end-to-end connectivity specifying how data should be packeted, addressed, transmitted, routed and received at the destination. This functionality is organized into four abstraction layers which are used to sort all related protocols according to the scope of networking involved.

Okay,

I'm pretty new to socket programming so I'd really just like some guidance here, specifically with C# .NET 4.5 Asynchronous Sockets.

I see the articles on MSDN but we all know those often aren't best practice, but just examples to see what "can" be done.

Can anyone advise on the best way to approach this?

Cheers!
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Is there a convenient (and ideally, free) substitute for TELNET for checking outbound TCP ports?
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I'm looking for software that can be set to respond to incoming packets on a certain port.

I need to run a test within my internal network to find out if certain ports (444, 3478, & 5061) are open and will respond to packets coming into the server on these ports.

This software needs to be compatible with Server 2008 R2.

What kind of software can do this?

Please let me know if any further information is needed.
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How an IP address could be addess to a blacklist ? MXtoolbox.
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We have a secure web site that verifies the IP address of the computer before it can authenticate to the web site.  Today two of our computers that previously had public IP addresses got new ones.  Today they had 50.97.211.199.  Previously they had 50.97.211.194.  These are from Softlayer.com.   How do we stop them from changing?
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Good Afternoon All

Due to expansion, we are moving part of our staff to another floor with a 2nd ISP. We are using (2) Dell Powerconnect 6224 switches as our gateways, one of the first floor and one on the second). Each floor is a separate network. They will be on the same domain just different IP subnets. All connection to internet are fine on both floors but having trouble getting the (2) floor to talk. Below is a rough layout of how I would like to it configured. All vlan should be able to talk back and forth. Any help would be great!

Thanks
Ed

Floor#2
--------------------------------------
192168.30.0/24 - Vlan1  
192.168.31.0/23 - Vlan2
192.168.33.0/24 - Vlan3
 -------------------------------------
                  |
             |6224|
                  |
VLAN999: 192.168.0.0/29
                  |
             |6224|
                  |
---------------------------------------
192.168.70.0/24 - VLAN1
192.168.71.0/23 - VLAN2
192.168.73.0/24 - VLAN3  
 ---------------------------------------
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A followup question to my earlier question:
http://www.experts-exchange.com/Networking/Protocols/Q_27949262.html

In that question, DavisMcCarn observed that:

"the wired machine is sending 80 times faster than the receiver and filling the memory buffer in the Trendnet creating the stall"

This could well be true, but maybe not.  The reason I think this may not be true is that when the device downloads the file through the AP, it takes several minutes and has an effective throughput of approximately 100KB/sec.

I can download that same file from the same server through the same AP using my Windows laptop rather than the "device" and the file downloads in a matter of seconds, at a rate closer to 4MB/sec.

If Windows7 can download the file at 4MB/sec, why would the AP "clog up" and introduce delays when the device is downloading the file at a mere 100KB/sec?
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I have a WLAN with a Cisco 2504 and 11 aironet 1140. Should i set within the Cisco 2504 static IP address for the Aironet AP or leave them dynamic?
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I am trying to get to the root cause of a five-second delay that occurs when a particular wireless device downloads a large file over a wireless network.  This delay happens occasionally during the downloading of large files.  Over the course of the download the delays accumulate to a lot of wasted time.

A thorough description of the situation is found in this related question:

http://www.experts-exchange.com/Networking/Protocols/Q_27948825.html

I am attaching a wireshark capture of an entire download.  This is a file being downloaded from a server (192.168.10.143) by a custom built hand-held network device (192.168.10.4).

One instance of a delay (or "gap") occurs in this capture file at:

#22496 at 18:13:47.4709 (1460 bytes of data)
#22503 at 18:13:47.4787 (1460 bytes of data)
#22695 at 18:13:52.4990 (588 bytes of data)   [ five seconds later! ]
#22700 at 18:13:52.5034 (1460 bytes of data)

The server appears to have simply stopped sending data for several seconds, and then when it did resume sending data, it started out with a smaller-than-usual packet.

What could have caused that lengthy delay?  Is there something wrong with the way the device is requesting or ACKing data?  I can perform this exact file transfer over the same network but to a Windows laptop instead of the "device" and the download doesn't seem to suffer from the same pauses/delays.

-----

My theory is that the device is doing something wrong or at least different from the windows…
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I have a situation I am trying to first understand, then diagnose.

In a nutshell, I've got a "device" which is having problems downloading a large file over a wireless network.  I want to first figure out what the device is doing wrong, then fix it.

overall I have four components:

> A TrendNET wireless "router" (broadcasting SSID='flash' on channel 6)
> A "Server" (WinXP) wired to the above router
> A Win7 "laptop" connected to 'flash' SSID
> A wireless "device" connected to 'flash' SSID

Using the laptop I can download a large file from the server over the wireless network and it works quickly and reliably.  This demonstrates that fast clean downloads are possible.

Then, using the device, I can download the same large file over the same wireless network.  This download is both slower and more prone to failure.  I want to discover why.

I have used wireshark to record both a download from the laptop and a download from the device.  There are certainly differences in the traffic, but I'm not familiar enough with packets to know what I'm looking at.

Can anyone tell me:

A ) Have I sufficiently explained the problem ?

and

B ) What expert services or individuals exist to analyze wireless packets and prescribe specific changes to address a problem like this ?

or

C ) What should I be looking at, or what further actions can I take to narrow down the problem and possibly diagnose this on my own?



WLAN NOTE:
These components are all nearby …
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One of our websites is being hit hard by some DOS attack.

Unfortunately the web developer did not use a captcha on the contact us page.

So my customer is getting massive spam - which all seems to come out of China (by IP address lookup).  It is going to be a few days before we get this feature added.

(NOTE - the same server is used to host an accounting application which uses a different TCP/IP Port for communication to the clients office.  There is quite a bit of data traffic that we do want to allow between server and our client's office).

I have two questions:

1) will this link work - to stop the spam?
        http://www.microsoft.com/en-au/download/details.aspx?id=29274 

2) How do I import ranges of IP addresses into IIS 7.5?
        (eg this website generates IP address ranges per country)
        http://www.ipaddresslocation.org/

    Further... should I get IP ranges or CIDR from this site?
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Hello,

I have installed IPv6 on an XP SP3 machine. Whilst I can successfully ping the machine using:-
ping6 ::1   or   ping6 fe80::e611:5bff:fe27:10b5

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I cannot browse to the local web site or web services using:-
 http://[::1]/myWebSite/logon.aspx  or http://[::1]/myWebService/myWebService.asmx

Open in new window

I can still reach these services using IPv4 by browsing to:-
http://localhost/myWebSite/logon.aspx  or  http://localhost/myWebService/myWebService.asmx

Open in new window

although if I edit my Hosts file to resolve localhost to ::1, this then fails also.

The web site uses net3.5 (ASP.net2). The web services use net1.1 and I have edited the machine.config to enable IPv6.

I have tried both IE8 and Chrome and get the same result. Can anyone advise how I can get IIS (version 5.1) to work with IPv6?

Many thanks in advance,
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How can I view the results of a ping command in iPv4 rather than iPv6?

It is becoming increasingly common when I ping a remote server's hostname to receive a response back in iPv6 rather than iPv4.

I am still learning iPv6 and need to be able to quickly determine the iPv4 addresses of remote servers.

Are there any command line switches that will allow me to view the results of what would be an iPv6 ping address in iPv4 instead?
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What happens if there is a "SMTP Reverse DNS Mismatch Warning - Reverse DNS does not match SMTP Banner" on my domain name?"

When I go to http://www.mxtoolbox.com and do an SMTP check of my company's external email address domain name, I get the results shown in the screenshot (see the screenshot).

I'm trying to figure out if this presents any problems or security issues with my domain (bayitnc.com) sending or receiving email.

Or might this cause issues with certain remote email servers where they won't accept emails from my domain because of this error?

Please let me know if any further info is needed.
Reverse-DNS-mismatch.png
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What sort of public DNS records do I need to add in order for Lync 2010 users to be able to use Lync on the public internet?

I have just installed a Lync 2010 server within a company's internal network. Everything work fine internally.

I have also installed a third party certificate for the Lync 2010 server.

However, when the users take their laptops outside of the company network, they are unable to establish a connection to our company's Lync server and are unable to send instant messages, make PC to PC phone calls, or make video calls.

I understand that there are other public DNS records that need to be added to the public internet to enable this capability.

Please provide me with a complete list of the public DNS records that need to be added.

Please let me know if any further information is needed.
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Have a very strange network issue that we can't seem to figure out. I have a 2-3 XP machines that are joined to Active Directory domain. Each machine has 2 nic's. Nic1 is connected to the domain network using DHCP. Nothing weird about the setup. Nic2 is connected to a private lab network (192.168.x.x) that is used for ping testing devices that use Windows CE. The two nic's are not bridged in any way. The application used to control the tested devices is served from a Windows 2003 server on the domain via shared folder on the server that is mapped to a local drive on the XP machine. The XP machine also has mapped network connections to 2 other shared folders on the same server as well as mapped printers to printer shares on another domain server. Everything was working great Friday.

When we came to work on Monday and booted the XP machine, the system could not connect to any of the mapped folders or printers. The user account is active and valid. We tried logging onto the XP machine using our domain admin access with no luck. The XP machine times out when trying to connect to any server on our domain (we have 4). It just times out and gives the "unable to connect" error. We can't even ping the server name or IP address. However, the XP machine will ping other systems in the domain without issue. And, I can connect to the Internet easily. Also, the servers cannot ping this machine, either!

It's as if there was something sitting between the client and the servers …
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Hello,

I have a network that has two VLANs.  VLAN 1 (default) and VLAN 2 (voice). All the switch ports are setup as Trunk ports Tagged on VLAN 2 and Untagged on VLAN 1.  Port e48 has a phone system connected to it and is it a Trunk port Untagged on VLAN 2.  In this configuration the phones on VLAN 2 can talk to the phone system but a laptop on VLAN1 cannot program the phone system...but can ping it.  If I switch port e48 to Tagged on VLAN2 and untagged on VLAN 1, a laptop can program the phone system but the phones don't come up.  This is a Dell PowerConnect 3524 switch.

Any thoughts?
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1) How do ip addresses get assigned to a host machine (linux and windows)?

2) If i have a linux machine with 1 apache web servers and another oracle http web server running on it, can i have one ip address assigned for web server 1 and another ip address for 2nd web server? How do you configure this.

3) if i log into a mahine, what command you run to see the ip addresss assigned?
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We have 2 "A" records for our company:

CompanyName.com
www.CompanyName.com

Can we delete "CompanyName.com"?  I don't think we need it.  What services will be lost?  Just to note our email is received using SMTP pump - a service provided by our ISP.  

I'm OK for http://companyname.com access to be removed because people can access our website through http://www.CompanyName.com.

Thanks
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I have tried a few and am disappointed.  Who can you recommend?

I plan to move my domains there.

Thanks.
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I am very disappointed with the company where I registered an important domain, which I will urgently need soon.  But worry it will be "in transit" when I need to launch my site.

How long is it supposed to take?

Are there risks of the domain becoming lost through incompetence?

Thanks.
0
Hello,

I have quite a few questions to ask about setting up a home or business network, but I should probably start with this one.

What should my internal network IP Addresses be? For years, I have been using 192.168.1.X because this is the suggested IP subnet recommended for home or business networks. But, recently a young acquaintenance who is in college, informed me that they traced my email or something and hacked into my network and used the 192.168.1.x subnet as a quess, and was able to get into my systems. This disturbs me.

So, besides having to review my firewall and stuff like that (I am going there next), I want to change my internal subnet to something different from what most devices default to.

For an internal network and for wireless access, what is a good IP address subnet to use and what rules should I follow when setting up internal IP addresses so that I don't  have problems with IP addresses in the Internet?

Thanks,
John
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Hello Experts

i have a physical windows 2008 R2 server with Symantec backup exec 2010 R3,
and for the last week or so i have an issue that the server keeps failing on backups.

but the reason for failing is probably the server NIC,
i get notification that the server is going offline every night at 3 PM,
and when i get in the office at morning, i need to do a "disable" and 'enable"
to the NIC in order to get it to work again.

i tried the followings:
1. upgrade the NIC driver
2. disable the save power option in the NIC properties

NOTE: the server is also used as the Vmware Vcenter.
any idea why this happening ?
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Hello

We have many domains within our forests, and also some seperate forests, within our environment, mainly due to mergers etc.

There is a domain named domain1.forest.com. We also have heavily used domains :

domain2.forest.com
domain1.otherforest.com
domain3.forest.com

There is an application server within Domain1 named APP1. This needs to talk to another server named APP2 (also in Domain2). However, the seems to be frequent errors in the event log of APP1 saying that it can't communicate with APP2.

I went to APP1 and tried to ping APP2. I got a "ping could not find this host" error. So I tried to ping APP2.domain1.forest.com and this worked.

I went to the Advanced TCP/IP settings of APP1 and noticed that within "Append these DNS suffixes", the order was;

dmain1.forest.com (i.e. spelt wrong)
domain2.forest.com
domain1.otherforest.com
domain3.forest.com

Could this result in errors? What exactly does this setting do?

Both servers are Windows 2008.
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Hi,

If my internal network is OSPF and we want to implement an MPLS VPN solution between our 7 sites, and the provider is requesting that we run the BGP protocol on our edge router to connect to the PE (providers edge), the labels will be popped at PE router.  That said, will that work if we configure BGP on our edge router (CE)?  If so, do I then on my edge router, do I need to figure out how to get my OSPF network to talk to the BGP side of the router?  I'm a little confused and doing a lot of reading but the day is going by fast and I'm not making progress here very swiftly, so figured I'd start asking questions.
Thanks,
R
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TCP/IP

11K

Solutions

17K

Contributors

Transmission Control Protocol/Internet Protocol (TCP/IP) is the set of networking protocols that define end-to-end connectivity specifying how data should be packeted, addressed, transmitted, routed and received at the destination. This functionality is organized into four abstraction layers which are used to sort all related protocols according to the scope of networking involved.