Can a TCP connection be made without an open port?

To continue reading for free, register below or login

Requires Membership to View

To gain access to this and all member only content, please provide the following information (all fields required):

First Name:
Last Name:
Country: Select... Afghanistan Aland Islands Albania Algeria American Samoa Andorra Angola Anguilla Antarctica Antigua and Barbuda Argentina Armenia Aruba Australia Austria Azerbaijan Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bermuda Bhutan Bolivia Bosnia and Herzegovina Botswana Bouvet Island Brazil British Indian Ocean Territory British Virgin Islands Brunei Bulgaria Burkina Faso Burundi Cambodia Cameroon Canada Cape Verde Cayman Islands Central African Republic Chad Chile China Christmas Island Cocos (Keeling) Islands Colombia Comoros Congo Congo, Democratic Republic of Cook Islands Costa Rica Cote D'Ivoire Croatia Cuba Cyprus Czech Republic Denmark Djibouti Dominica Dominican Republic Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Ethiopia Falkland Islands Faroe Islands Fiji Finland France French Guiana French Polynesia French Southern Territories Gabon Gambia, The Georgia Germany Ghana Gibraltar Greece Greenland Grenada Guadeloupe Guam Guatemala Guernsey Guinea Guinea-Bissau Guyana Haiti Heard and McDonald Islands Honduras Hong Kong Hungary Iceland India Indonesia Iran Iraq Ireland Israel Italy Jamaica Japan Jersey Jordan Kazakhstan Kenya Kiribati Korea, North Korea, South Kuwait Kyrgyzstan Laos Latvia Lebanon Lesotho Liberia Libya Liechtenstein Lithuania Luxembourg Macau Macedonia Madagascar Malawi Malaysia Maldives Mali Malta Man, Isle of Marshall Islands Martinique Mauritania Mauritius Mayotte Mexico Micronesia Moldova Monaco Mongolia Montserrat Morocco Mozambique Myanmar Namibia Nauru Nepal Netherlands Netherlands Antilles New Caledonia New Zealand Nicaragua Niger Nigeria Niue Norfolk Island Northern Mariana Islands Norway Oman Pakistan Palau Palestine Panama Panama Canal Zone Papua New Guinea Paraguay Peru Philippines Pitcairn Poland Portugal Puerto Rico Qatar Reunion Romania Russia Rwanda Saint Helena Saint Kitts and Nevis Saint Lucia Saint Pierre and Miquelon Saint Vincent and the Grenadines Samoa San Marino Sao Tome and Principe Saudi Arabia Senegal Serbia and Montenegro Seychelles Sierra Leone Singapore Slovakia Slovenia Solomon Islands Somalia South Africa South Georgia and South Sandwich Islands Spain Sri Lanka Sudan Suriname Svalbard Swaziland Sweden Switzerland Syria Taiwan Tajikistan Tanzania Thailand Timor-Leste Togo Tokelau Tonga Trinidad and Tobago Tunisia Turkey Turkmenistan Turks and Caicos Islands Tuvalu U.S. Minor Outlying Islands Uganda Ukraine United Arab Emirates United Kingdom United States Uruguay Uzbekistan Vanuatu Vatican City Venezuela Vietnam Virgin Islands Wallis and Futuna Islands Western Sahara Yemen Zambia Zimbabwe
Email Address:

I would like to receive a FREE subscription to Information Security magazine online.
YesNo

Do you manage, evaluate, recommend, implement, support or purchase security products, software or services?
YesNo

Please estimate the yearly security budget for your entire organization including all security products and services.
Please select... Over $10 Million $5 Million-$10 Million $1 Million-$4.9 Million $500,000-$999,999 $100,000-$499,999 $50,000-$99,999 $25,000-$49,999 $10,000-$24,999 Less than $10,000 None

What is your role in purchasing IT related products and services? (Check all that apply)
Technical decision maker
Financial decision maker
Recommend/Specify
Evaluate products
Implement Products/Services
Determine Needs
Create Security Strategy
None

By joining SearchSecurity.com you agree to receive email updates from the TechTarget network of sites, including updates on new content, magazine or event notifications, new site launches and market research surveys. Please verify all information and selections above. You may unsubscribe at any time from one or more of the services you have selected by editing your profile or unsubscribing via email.

TechTarget cares about your privacy. Read our Privacy Policy

BROWSE BY TAG Network Security,   Network Protocols and Security,   Enterprise Network Security,   VIEW ALL TAGS

Digg This!     StumbleUpon     Del.icio.us

RELATED CONTENT Network Security Should enterprises be running multiple firewalls? What are best practices for fiber optic cable security? What is the difference between a VPN and remote control? What are the disadvantages of proxy-based firewalls? What are the best practices for IPS implementation? How to prevent DDoS attacks on websites How to configure firewall ports for webmail system implementation Can S/MIME, XML and IPsec operate in one protocol layer? How should service providers address VoIP security issues and threats? How to set up a corporate cell phone management strategy Network Protocols and Security Kaminsky interview: DNSSEC addresses cross-organizational trust and security PCI compliance requirement 4: Encrypt transmissions Balancing security and performance: Protecting layer 7 on the network Swedish hacker indicted for Cisco Systems, NASA breach How to implement PCI network segmentation How should service providers address VoIP security issues and threats? How to create a secure network through a shared Internet connection Cyberattack mapping could alter security defense strategy The case against UTM: Is there a better alternative? What is the best operating system for an FTP server implementation?

RELATED GLOSSARY TERMS Terms from Whatis.com − the technology online dictionary 5 terms you need to know before you employ VoIP  (SearchSecurity.com) digest authentication  (SearchSecurity.com) IGP  (SearchSecurity.com) IP spoofing  (SearchSecurity.com) Secure Sockets Layer  (SearchSecurity.com) smurfing  (SearchSecurity.com) Transport Layer Security  (SearchSecurity.com)

RELATED RESOURCES 2020software.com, trial software downloads for accounting software, ERP software, CRM software and business software systems Search Bitpipe.com for the latest white papers and business webcasts Whatis.com, the online computer dictionary

You didn't provide the name of the product, so I can't evaluate this specific application. What you're describing, however, isn't possible. I suspect that the manufacturer is playing some word games to hype their product. Let's explore why.

Two computers communicate over the Internet by using their IP addresses and a combination of ports. The client computer (the one requesting the connection) contacts the server on a known destination port and provides the server with its own IP address and a source port that the server may use for reply traffic. All communication then takes place using those source/destination port and address combinations.

In order for the computers to communicate successfully, the server must have at least one port open to receive inbound requests. The client must then open the source port for replies from that particular system. That's simply the only way that a TCP connection can take place (UDP traffic is slightly different, but follows the same basic idea).

I suspect what the product you describe actually does is swap the client and server roles from their traditional sense. The server and client may both establish a connection to an intermediary server that routes traffic between the two. However, there's simply no way that this can be accomplished without some kind of device listening for traffic on a known port.

More information: