Locally forward tcp port bidirectional











up vote
0
down vote

favorite












I wonder how it is possible to locally forward a tcp port, bidirectional, i. e. all packets leaving the local machine on port 25 (this port of course is actually dynamically assigned) should be rewritten to have a source port of e. g. 500 (thats the part I dont know how to do), and all ports coming in on port 500 should be forwarded to port 25 (I know how to do this).

In consequence, a daemon listening on port 25 would be happy, while all destinations would believe the daemon is listening on port 500. Correct me if I am wrong.






linux iptables tcp port-forwarding







share|improve this question




























    up vote
    0
    down vote

    favorite












    I wonder how it is possible to locally forward a tcp port, bidirectional, i. e. all packets leaving the local machine on port 25 (this port of course is actually dynamically assigned) should be rewritten to have a source port of e. g. 500 (thats the part I dont know how to do), and all ports coming in on port 500 should be forwarded to port 25 (I know how to do this).

    In consequence, a daemon listening on port 25 would be happy, while all destinations would believe the daemon is listening on port 500. Correct me if I am wrong.






    linux iptables tcp port-forwarding







    share|improve this question


























      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      I wonder how it is possible to locally forward a tcp port, bidirectional, i. e. all packets leaving the local machine on port 25 (this port of course is actually dynamically assigned) should be rewritten to have a source port of e. g. 500 (thats the part I dont know how to do), and all ports coming in on port 500 should be forwarded to port 25 (I know how to do this).

      In consequence, a daemon listening on port 25 would be happy, while all destinations would believe the daemon is listening on port 500. Correct me if I am wrong.






      linux iptables tcp port-forwarding







      share|improve this question















      I wonder how it is possible to locally forward a tcp port, bidirectional, i. e. all packets leaving the local machine on port 25 (this port of course is actually dynamically assigned) should be rewritten to have a source port of e. g. 500 (thats the part I dont know how to do), and all ports coming in on port 500 should be forwarded to port 25 (I know how to do this).

      In consequence, a daemon listening on port 25 would be happy, while all destinations would believe the daemon is listening on port 500. Correct me if I am wrong.






      linux iptables tcp port-forwarding




      linux iptables tcp port-forwarding






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited yesterday









      Rui F Ribeiro

      38.6k1479128




      38.6k1479128










      asked Nov 2 at 14:44









      L. Riemer

      11




      11






















          1 Answer
          1






          active

          oldest

          votes

















          up vote
          1
          down vote













          When you redirect port 25 to port 500, you don't need to redirect port 500 to port 25 again. NAT works with connections and it will handle return packets for you.



          For example try to redirect port 23 to port 22 which ssh is listening 



          iptables -t nat -A PREROUTING -p tcp --dport 23 -j REDIRECT --to-port 22


          Now you can connect that device via port 23



          ssh foo@mysshserver -p 23


          In your case you should add this rule



          iptables -t nat -A PREROUTING -p tcp --dport 500 -j REDIRECT --to-port 25


          Now all client are able to connect via port 500 to daemon which is listening port 25






          share|improve this answer























            Your Answer








            StackExchange.ready(function() {
            var channelOptions = {
            tags: "".split(" "),
            id: "106"
            };
            initTagRenderer("".split(" "), "".split(" "), channelOptions);

            StackExchange.using("externalEditor", function() {
            // Have to fire editor after snippets, if snippets enabled
            if (StackExchange.settings.snippets.snippetsEnabled) {
            StackExchange.using("snippets", function() {
            createEditor();
            });
            }
            else {
            createEditor();
            }
            });

            function createEditor() {
            StackExchange.prepareEditor({
            heartbeatType: 'answer',
            convertImagesToLinks: false,
            noModals: true,
            showLowRepImageUploadWarning: true,
            reputationToPostImages: null,
            bindNavPrevention: true,
            postfix: "",
            imageUploader: {
            brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
            contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
            allowUrls: true
            },
            onDemand: true,
            discardSelector: ".discard-answer"
            ,immediatelyShowMarkdownHelp:true
            });


            }
            });














            draft saved

            draft discarded


















            StackExchange.ready(
            function () {
            StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2funix.stackexchange.com%2fquestions%2f479412%2flocally-forward-tcp-port-bidirectional%23new-answer', 'question_page');
            }
            );

            Post as a guest















            Required, but never shown

























            1 Answer
            1






            active

            oldest

            votes








            1 Answer
            1






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes








            up vote
            1
            down vote













            When you redirect port 25 to port 500, you don't need to redirect port 500 to port 25 again. NAT works with connections and it will handle return packets for you.



            For example try to redirect port 23 to port 22 which ssh is listening 



            iptables -t nat -A PREROUTING -p tcp --dport 23 -j REDIRECT --to-port 22


            Now you can connect that device via port 23



            ssh foo@mysshserver -p 23


            In your case you should add this rule



            iptables -t nat -A PREROUTING -p tcp --dport 500 -j REDIRECT --to-port 25


            Now all client are able to connect via port 500 to daemon which is listening port 25






            share|improve this answer



























              up vote
              1
              down vote













              When you redirect port 25 to port 500, you don't need to redirect port 500 to port 25 again. NAT works with connections and it will handle return packets for you.



              For example try to redirect port 23 to port 22 which ssh is listening 



              iptables -t nat -A PREROUTING -p tcp --dport 23 -j REDIRECT --to-port 22


              Now you can connect that device via port 23



              ssh foo@mysshserver -p 23


              In your case you should add this rule



              iptables -t nat -A PREROUTING -p tcp --dport 500 -j REDIRECT --to-port 25


              Now all client are able to connect via port 500 to daemon which is listening port 25






              share|improve this answer

























                up vote
                1
                down vote










                up vote
                1
                down vote









                When you redirect port 25 to port 500, you don't need to redirect port 500 to port 25 again. NAT works with connections and it will handle return packets for you.



                For example try to redirect port 23 to port 22 which ssh is listening 



                iptables -t nat -A PREROUTING -p tcp --dport 23 -j REDIRECT --to-port 22


                Now you can connect that device via port 23



                ssh foo@mysshserver -p 23


                In your case you should add this rule



                iptables -t nat -A PREROUTING -p tcp --dport 500 -j REDIRECT --to-port 25


                Now all client are able to connect via port 500 to daemon which is listening port 25






                share|improve this answer














                When you redirect port 25 to port 500, you don't need to redirect port 500 to port 25 again. NAT works with connections and it will handle return packets for you.



                For example try to redirect port 23 to port 22 which ssh is listening 



                iptables -t nat -A PREROUTING -p tcp --dport 23 -j REDIRECT --to-port 22


                Now you can connect that device via port 23



                ssh foo@mysshserver -p 23


                In your case you should add this rule



                iptables -t nat -A PREROUTING -p tcp --dport 500 -j REDIRECT --to-port 25


                Now all client are able to connect via port 500 to daemon which is listening port 25







                share|improve this answer














                share|improve this answer



                share|improve this answer








                edited Nov 9 at 10:14

























                answered Nov 6 at 19:01









                ibrahim

                392212




                392212






























                    draft saved

                    draft discarded




















































                    Thanks for contributing an answer to Unix & Linux Stack Exchange!


                    • Please be sure to answer the question. Provide details and share your research!

                    But avoid …



                    • Asking for help, clarification, or responding to other answers.

                    • Making statements based on opinion; back them up with references or personal experience.


                    To learn more, see our tips on writing great answers.





                    Some of your past answers have not been well-received, and you're in danger of being blocked from answering.


                    Please pay close attention to the following guidance:


                    • Please be sure to answer the question. Provide details and share your research!

                    But avoid …



                    • Asking for help, clarification, or responding to other answers.

                    • Making statements based on opinion; back them up with references or personal experience.


                    To learn more, see our tips on writing great answers.




                    draft saved


                    draft discarded














                    StackExchange.ready(
                    function () {
                    StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2funix.stackexchange.com%2fquestions%2f479412%2flocally-forward-tcp-port-bidirectional%23new-answer', 'question_page');
                    }
                    );

                    Post as a guest















                    Required, but never shown





















































                    Required, but never shown














                    Required, but never shown












                    Required, but never shown







                    Required, but never shown

































                    Required, but never shown














                    Required, but never shown












                    Required, but never shown







                    Required, but never shown







                    -

                    Popular posts from this blog

                    サソリ

                    Image
                    この記事は検証可能な参考文献や出典が全く示されていないか、不十分です。 出典を追加して記事の信頼性向上にご協力ください。 （ 2019年1月 ） 「 サソリ 」のその他の用法については「サソリ (曖昧さ回避)」をご覧ください。 「 スコーピオン 」と「 スコルピオン 」はこの項目へ転送されています。その他の用法については「スコーピオン」をご覧ください。 サソリ目 生息年代: 430–0 Ma PreЄ Є O S D C P T J K Pg N シルル紀前期-現世 ダイオウサソリ（ Pandinus Imperator ） 分類 界 : 動物界 Animalia 門 : 節足動物門 Arthropoda 亜門 : 鋏角亜門 Chelicerata 綱 : クモガタ綱 Arachnida 目 : サソリ目 Scorpiones 学名 Scorpiones C. L. Koch, 1837 英名 Scorpion 上科 Pseudochactoidea キョクトウサソリ上科 Buthoidea Chaeriloidea Chactoidea Iuroidea Scorpionoidea サソリ （ サソリ類 、 蠍 、 蝎 、 scorpion ）は、鋏角亜門・クモガタ綱の サソリ目 （ Scorpiones ）に属する節足動物の総称である。体の前端に鋏型の触肢、後端に毒針を有する捕食者である。 1700種以上を含め、最古の化石記録は4億3千万年前のシルル紀まで遡る。有毒生物として広く知られるが、人間の命にかかわる毒を持つものはごく一部の種類に過ぎない。 目次 1 形態 1.1 前体 1.2 後体 1.2.1 中体 1.2.2 終体 2 雌雄 3 生態 3.1 天敵 3.2 生殖 4 分布 5 毒 6 蛍光現象 7 分類
                    Read more

                    広島県道265号伴広島線

                    Image
                    一般県道 広島県道265号伴広島線 路線延長 km 起点 広島県広島市安佐南区伴東7丁目 終点 広島県広島市中区榎町 接続する 主な道路 （記法） 広島県道38号広島豊平線 広島県道71号広島湯来線 山陽自動車道五日市IC 国道183号（ 国道261号重複） ■テンプレート（■ノート ■使い方） ■PJ道路 広島県道265号伴広島線 （ひろしまけんどう265ごう ともひろしません）は広島県広島市安佐南区から広島県広島市中区を結ぶ一般県道である。 目次 1 路線データ 2 通過する自治体 3 見どころ 4 接続道路 4.1 本線 4.2 旧道 5 別名 6 関連項目 路線データ 本線 起点：広島市安佐南区伴東7丁目・大原下橋南詰交差点（広島県道38号広島豊平線（本線・旧道）交点） 終点：広島市中区榎町・十日市交差点（国道183号（国道261号重用）交点） 総延長： 旧道 起点：広島市安佐南区伴東4丁目・新細坂交差点（広島県道38号広島豊平線交点） 終点：広島市安佐南区伴中央4丁目・寺組橋(南)交差点（広島県道265号伴広島線（本線）交点） 総延長： 通過する自治体 広島県 広島市（安佐南区、佐伯区、西区、中区） 見どころ 広島高速交通広島新交通1号線（アストラムライン） 広島広域公園 広島広域公園陸上競技場（広島ビッグアーチ） 己斐峠 己斐橋（太田川放水路） 天満橋（天満川） 接続道路 本線 広島県道38号広島豊平線（本線・旧道）（広島市安佐南区伴東7丁目・大原下橋南詰交差点〔起点〕） 広島県道71号広島湯来線（本線）（広島市安佐南区伴中央2丁目・伴交番入口交差点 - 広島市安佐南区伴中央4丁目・寺組橋(南)交差点間で重用） 広島県道71号広島湯来線（旧道）（広島県道265号伴広島線（旧道）重用）（広島市安佐南区伴中央4丁目・寺組橋(南)交差点） 広島県道71号広島湯来線（広島市安佐南区伴中央4丁目・寺組橋(南)交差点 - 広島市佐伯区五日市町石内・五月が丘(南)交差点間で重用）
                    Read more

                    Setup Asymptote in Texstudio

                    Image
                    0 Good time of the day! I am trying to compile the following file: documentclass[12pt]{article} usepackage[inline]{asymptote} begin{document} Here is a venn diagram produced with Asymptote, drawn to width 4cm: defA{A} defB{V{B}} begin{figure} begin{center} begin{asy} size(4cm,0); pen colour1=red; pen colour2=green; pair z0=(0,0); pair z1=(-1,0); pair z2=(1,0); real r=1.5; path c1=circle(z1,r); path c2=circle(z2,r); fill(c1,colour1); fill(c2,colour2); picture intersection=new picture; fill(intersection,c1,colour1+colour2); clip(intersection,c2); add(intersection); draw(c1); draw(c2); //draw("$A$",box,z1)
                    Read more