What Is TCP/IP
TCP/IP
(Transmission Control Protocol/Internet Protocol) A communications protocol developed under contract from the U.S. Department of Defense to internetwork dissimilar systems. Invented by Vinton Cerf and Bob Kahn, this de facto Unix standard is the protocol of the Internet and has become the global standard for communications.
TCP provides transport functions, which ensures that the total amount of bytes sent is received correctly at the other end. UDP, which is part of the TCP/IP suite, is an alternate transport that does not guarantee delivery. It is widely used for realtime voice and video transmissions where erroneous packets are not retransmitted.
TCP/IP is a routable protocol, and the IP part of TCP/IP provides this capability. In a routable protocol, all messages contain not only the address of the destination station, but the address of a destination network. This allows TCP/IP messages to be sent to multiple networks (subnets) within an organization or around the world, hence its use in the worldwide Internet.
The IP network layer (layer 3) of the TCP/IP protocol stack accepts packets from the TCP or UDP transport layer (layer 4), adds its own header and delivers a "datagram" to the data link layer protocol (layer 2).
Every client and server in a TCP/IP network requires an IP address, which is either permanently assigned or dynamically assigned at startup.
For an explanation of how the various layers in TCP/IP work, see TCP/IP abc's and TCP/IP port. See also IP address, NFS, NIS, DNS, DHCP, dumb network and IP on Everything.
Description Of The Portqry.Exe Command-Line Utility For TCP/IP
This article was previously published under Q310099
Portqry.exe is a command-line utility that you can use to help troubleshoot TCP/IP connectivity issues.
Portqry.exe runs on Windows 2000-based computers, on Windows XP-based computers, and on Windows Server 2003-based computers. The utility reports the port status of TCP and UDP ports on a computer that you select.
Note Version 2 of Portqry.exe is now available. The Microsoft Download Center link at the end of this article has been updated to reflect the new version. Version 1.0 of Portqry.exe has been removed from the Microsoft Download Center.
Portqry.exe reports the status of a TCP/IP port in one of the following three ways:
• Listening
A process is listening on the port on the computer that you selected. Portqry.exe received a response from the port.
• Not Listening
No process is listening on the target port on the target system. Portqry.exe received an Internet Control Message Protocol (ICMP) "Destination Unreachable - Port Unreachable" message back from the target UDP port. Or if the target port is a TCP port, Portqry received a TCP acknowledgement packet with the Reset flag set.
• Filtered
The port on the computer that you selected is being filtered. Portqry.exe did not receive a response from the port. A process may or may not be listening on the port. By default, TCP ports are queried three times, and UDP ports are queried one time before a report indicates that the port is filtered.
Portqry.exe can query a single port, an ordered list of ports, or a sequential range of ports.
Examples
The following command tries to resolve "reskit.com" to an IP address and then queries TCP port 25 on the corresponding host:
portqry -n reskit.com -p tcp -e 25
The following command tries to resolve "169.254.0.11" to a host name and then queries TCP ports 143,110, and 25 (in that order) on the host that you selected. This command also creates a log file (Portqry.log) that contains a log of the command that you ran and its output.
portqry -n 169.254.0.11 -p tcp -o 143,110,25 -l portqry.log
The following command tries to resolve my_server to an IP address and then queries the specified range of UDP ports (135-139) in sequential order on the corresponding host. This command also creates a log file (my_server.txt) that contains a log of the command that you ran and its output.
portqry -n my_server -p udp -r 135:139 -l my_server.txt
Portqry.exe is available for download from the Microsoft Download Center. To download Portqry.exe, visit the following Microsoft Web site:
http://www.microsoft.com/downloads/details.aspx?familyid=89811747-C74B-4638-A2D5-AC828BDC6983&displaylang=en
Important The PortQueryUI tool provides a graphical user interface and is available for download.
PortQueryUI has several features that can make using PortQry easier. To obtain the PortQueryUI tool, visit the following Microsoft Web site:
http://download.microsoft.com/download/3/f/4/3f4c6a54-65f0-4164-bdec-a3411ba24d3a/PortQryUI.exe
For additional information about PortQry version 2.0, click the following article number to view the article in the Microsoft Knowledge Base:
http://support.microsoft.com/?kbid=832919
New features and functionality in PortQry version 2.0
For additional information about related topics, click the following article numbers to view the articles in the Microsoft Knowledge Base:
http://support.microsoft.com/?kbid=310298
How to use Portqry.exe to troubleshoot Microsoft Exchange Server connectivity issues
http://support.microsoft.com/?kbid=310456
How to use Portqry to troubleshoot Active Directory connectivity issues
http://support.microsoft.com/?kbid=832017
Port requirements for the Microsoft Windows Server System
http://support.microsoft.com/?kbid=325494
Support WebCast: port scanning using PortQry
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APPLIES TO
• Microsoft Windows Small Business Server 2003 Premium Edition
• Microsoft Windows Small Business Server 2003 Standard Edition
• Microsoft Windows Server 2003, Standard Edition
• Microsoft Windows Server 2003, Enterprise Edition
• Microsoft Windows XP Home Edition
• Microsoft Windows XP Professional Edition
• Microsoft Windows 2000 Server
• Microsoft Windows 2000 Advanced Server
• Microsoft Windows 2000 Professional Edition
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