{"id":239137,"date":"2025-07-02T18:24:38","date_gmt":"2025-07-02T18:24:38","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=239137"},"modified":"2025-07-02T18:24:40","modified_gmt":"2025-07-02T18:24:40","slug":"what-tcp-flags-is-are-replied-from-a-server-if-a-port-is-open","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/07\/02\/what-tcp-flags-is-are-replied-from-a-server-if-a-port-is-open\/","title":{"rendered":"What TCP flag(s) is\/are replied from a server if a port is open"},"content":{"rendered":"\n

What TCP flag(s) is\/are replied from a server if a port is open? SYN, ACK RST, ACK SYN ACK<\/p>\n\n\n\n

The correct answer and explanation is:<\/mark><\/strong><\/p>\n\n\n\n

The correct answer is SYN, ACK<\/strong>.<\/p>\n\n\n\n

Explanation:
When a client attempts to initiate a TCP connection to a server, it starts with a “SYN” request to the server, signaling the desire to establish a connection. This is the first step in the TCP three-way handshake.<\/p>\n\n\n\n

If the server’s port is open and it is ready to accept connections, the server will respond with a SYN-ACK<\/strong>. This means the server acknowledges the client’s “SYN” request and signals that it is willing to establish the connection. The SYN flag is set to indicate the server’s willingness to initiate a session, while the ACK flag confirms that the server received the client’s request.<\/p>\n\n\n\n

Here’s how the handshake unfolds in detail:<\/p>\n\n\n\n

    \n
  1. SYN (client to server):<\/strong> The client sends a TCP packet with the SYN flag set to start the connection. This means “I want to communicate, and I am starting the process.”<\/li>\n\n\n\n
  2. SYN-ACK (server to client):<\/strong> If the server is ready and the port is open, it replies with a TCP packet that has both the SYN and ACK flags set. The SYN flag indicates the server\u2019s intent to establish a session, and the ACK flag acknowledges the receipt of the client\u2019s SYN packet.<\/li>\n\n\n\n
  3. ACK (client to server):<\/strong> Finally, the client responds with an ACK packet, confirming the establishment of the connection.<\/li>\n<\/ol>\n\n\n\n

    If the server\u2019s port is closed, a different flag, RST (reset)<\/strong>, may be sent, indicating the port is not available for communication. The server sends a RST, ACK<\/strong> response to the client, signaling that the connection attempt is not permitted.<\/p>\n\n\n\n

    Therefore, SYN, ACK<\/strong> is the correct flag combination sent by the server when the port is open and ready to establish a TCP connection.<\/p>\n","protected":false},"excerpt":{"rendered":"

    What TCP flag(s) is\/are replied from a server if a port is open? SYN, ACK RST, ACK SYN ACK The correct answer and explanation is: The correct answer is SYN, ACK. Explanation:When a client attempts to initiate a TCP connection to a server, it starts with a “SYN” request to the server, signaling the desire […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[25],"tags":[],"class_list":["post-239137","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/239137","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/comments?post=239137"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/239137\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=239137"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=239137"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=239137"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}