ittagnelli · Costanzo-Francesco · Oct 28, 2025 · Oct 28, 2025 · Oct 29, 2025 · Oct 29, 2025
diff --git a/TPSI/costanzo_francesco/.gitignore b/TPSI/costanzo_francesco/.gitignore
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+**/.idea/
diff --git a/TPSI/costanzo_francesco/.gitkeep b/TPSI/costanzo_francesco/.gitkeep
diff --git a/TPSI/costanzo_francesco/css/esercizio_css_18/costanzo_esercizio_css_18.css b/TPSI/costanzo_francesco/css/esercizio_css_18/costanzo_esercizio_css_18.css
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+div {
+    background-color: lightblue;
+    color:navy;
+    border-top: 15px solid navy;
+    border-bottom: 15px solid navy;
+ }
+
+ #div1 {
+   width: 100px;
+   padding: 25px;
+   border: 25px solid navy;
+   margin-bottom: 2rem;
+ }
+
+ #div2 {
+   width: 250px;
+   padding-left: 15px;
+   padding-right: 10px;
+   border-left: 10px solid navy;
+   border-right: 15px solid navy;
+   margin-bottom: 2rem;
+ }
+
+ #div3 {
+   width: 353px;
+   padding-left: 1px;
+   padding-right: 19px;
+   border-left: 14px solid navy;
+   border-right: 21px solid navy;
+ }
diff --git a/TPSI/costanzo_francesco/css/esercizio_css_18/costanzo_esercizio_css_18.html b/TPSI/costanzo_francesco/css/esercizio_css_18/costanzo_esercizio_css_18.html
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+<!DOCTYPE html>
+<html lang="it"><head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <link rel="stylesheet" href="costanzo_esercizio_css_18.css" type="text/css">
+    <title>Esercizio 18</title><!-- titolo della pagina -->
+</head>
+<body>
+  <div id="div1">Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.</div>
+  <div id="div2">Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.</div>
+  <div id="div3">Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.</div>
+</body>
+</html>
diff --git a/TPSI/costanzo_francesco/css/esercizio_css_19/costanzo_esercizio_css_19.css b/TPSI/costanzo_francesco/css/esercizio_css_19/costanzo_esercizio_css_19.css
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+h1 {
+    border-bottom: solid 5px blue;
+    border-left: solid 2px green;
+}
+
+h2{
+    border-top: dashed 2px green;
+}
+
+p{
+    border-bottom: dashed 3px grey;
+    border-left: solid 1px green;
+    border-right:   solid 1px green;
+}
diff --git a/TPSI/costanzo_francesco/css/esercizio_css_19/costanzo_esercizio_css_19.html b/TPSI/costanzo_francesco/css/esercizio_css_19/costanzo_esercizio_css_19.html
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+<!DOCTYPE html>
+<html lang="in">
+  <head>
+    <meta charset="UTF-8" />
+    <meta name="author" content="Francesco Costanzo" />
+    <title>local host</title>
+
+    <link https://en.wikipedia.org/wiki/Localhost>
+    <link href="./costanzo_esercizio_css_19.css" rel="stylesheet" type="text/css">
+  </head>
+  <body>
+    <h1>Localhost</h1>
+    <p>
+      The local loopback mechanism may be used to run a network service on a
+      host without requiring a physical network interface, or without making the
+      service accessible from the networks the computer may be connected to. For
+      example, a locally installed website may be accessed from a Web browser by
+      the URL http://localhost to display its home page. The name localhost
+      normally resolves to the <abbr title="Internet Protocol version 4">IPv4</abbr> loopback address 127.0.0.1, and to the 
+      <abbr title="Internet Protocol version 5">IPv6</abbr>
+      loopback address ::1. <br>
+
+      <cite>“I computer sono incredibilmente veloci, accurati e stupidi. Gli uomini sono incredibilmente lenti,
+         inaccurati e intelligenti. L'insieme dei due costituisce una forza incalcolabile.”</cite><br>Albert Einstain
+    </p>
+
+    <h2>Loopback</h2>
+    <p>
+      IPv4
+      <a href="https://it.wikipedia.org/wiki/Network" target="_blank"
+        >network</a
+      >
+      standards <span style="color: red">reserve</span> the entire address block
+      127.0.0.0/8 (more than 16 million addresses) for loopback purposes.[2]
+      That means any packet sent to any of those addresses is looped back. The
+      address 127.0.0.1 is the standard address for IPv4
+      <a
+        href="https://it.wikipedia.org/wiki/Interfaccia_di_loopback"
+        target="_blank"
+        >loopback</a>
+      traffic; the rest are not supported by <s>all</s> operating systems. However,
+      they can be used to set up multiple server applications on the host, all
+      listening on the same port number. The IPv6 standard assigns only a single
+      address for loopback: ::1. The resolution of the name localhost to one or
+      more IP addresses is normally configured by the following lines in the
+      operating system's hosts file:IPv4 network standards reserve the entire
+      address block 127.0.0.0/8 (more than 16 million addresses) for loopback
+      purposes.[2] That means <span style="color: blue">any packet</span> sent
+      to any of those addresses is looped back. The address 127.0.0.1 is the
+      standard address for IPv4 loopback traffic; the rest are not supported by
+      all operating systems. However, they can be used to set up multiple server
+      applications on the host, all listening on the same <s>port number</s>. The IPv6
+      standard assigns only a single address for loopback: ::1. The resolution
+      of the name localhost to one or more IP addresses is normally configured
+      by the following lines in the operating system's hosts file: <br />
+      127.0.0.1 localhost<br />
+      ::1 localhost<br />
+      127.0.0.1 localhost<br />
+      ::1 localhost
+      <br /><br />
+      <img
+        src="https://www.computernetworkingnotes.com/wp-content/uploads/networking-tutorials/images/it04-01-ipv-6-structure-and-format.PNG"
+        alt="immagine ipv6, esempio"
+      />
+      <br />
+      The name may also be resolved by Domain Name System (DNS) servers, but
+      queries for this name should be resolved locally, and should not be
+      forwarded to remote name servers. <br />
+      <br />
+      In addition to the mapping of localhost to the loopback addresses
+      (127.0.0.1 and ::1), localhost may also be mapped to other IPv4 (loopback)
+      addresses and it is also possible to assign other, or additional, names to
+      any loopback address. The mapping of localhost to addresses other than the
+      designated loopback address range in the hosts file or in DNS is not
+      guaranteed to have the desired effect, as applications may map the name
+      internally.
+      <br /><br />
+      In the Domain Name
+      <a
+        href="https://it.wikipedia.org/wiki/Sistema_informatico"
+        target="_blank"
+        >System</a
+      >, the name localhost is reserved as a top-level domain name, originally
+      set aside to avoid confusion with the hostname used for loopback
+      purposes.[3] IETF standards prohibit domain name registrars from assigning
+      the name localhost.
+    </p>
+
+    <h2>IETF standards</h2>
+    <img src="./ietf.jpeg" alt="immagine ietf" />
+
+    <p>
+      The name localhost is reserved for loopback purposes by RFC 6761
+      (Special-Use Domain Names),[4] which achieved the Proposed Standard
+      maturity level in February 2013. The standard sets forth a number of
+      special considerations governing the use of the name in the Domain Name
+      System: <br />
+      <br />
+
+
+      An <u>IPv4</u> or <u>IPv6</u> address query for the name localhost must always resolve
+      to the respective loopback address, which is specified in a separate
+      standard. Applications may resolve the name to a loopback address
+      themselves, or pass it to the local name resolver mechanisms. When a name
+      resolver receives an address (A or AAAA) <s>query</s> for localhost, it should
+      return the appropriate loopback addresses, and negative responses for any
+      other requested record types. Queries for localhost should not be sent to
+      caching name servers. To avoid burdening the <s>Domain</s> Name System root
+      servers with traffic, caching name servers should never request name
+      server records for localhost, or forward resolution to authoritative name
+      servers. DNS registrars are precluded from delegating domain names in the
+      top-level domain localhost. When
+      <span style="color: green">name servers</span> receive queries for
+      'localhost' in spite of the provisions mentioned resolve them
+      appropriately. The IPv4 loopback addresses are reserved within the IPv4
+      address space by the <q>IETF</q> "Special Use IPv4 Addresses" standard (RFC
+      5735).[5] The reservation can be traced back to the November 1986
+      "Assigned Numbers" standard (RFC 990).
+      <blockquote cite ="https://www.frasicelebri.it/frasi-di/john-von-neumann/">
+        “Chiunque consideri i metodi aritmetici metodi di produrre numeri casuali è, naturalmente, in uno stato di peccato.”
+      </blockquote>
+      <br />
+      <br />
+      In contrast, the
+      <a
+        href="https://it.wikipedia.org/wiki/Internet_Engineering_Task_Force"
+        target="_blank"
+        >IETF</a
+      >
+      "IP Version 6 Addressing Architecture" <s>standard</s> (RFC 4291) reserves the
+      single IPv6 loopback address ::1 within the IPv6 address space. The
+      standard precludes the assignment of that address to any physical
+      interface, as well as its use as the source or destination address in any
+      packet sent to remote hosts. Any such packet that is erroneously
+      transmitted is not supposed to be routed, and should be dropped by all
+      routers or hosts that receive it.
+    </p>
+    <code>sudo pacman -S IETF</code>
+    <pre>Quest'ultimo è un comando inutile che non funziona</pre>
+
+    <h2>Packet processing</h2>
+    <a href="https://en.wikipedia.org/wiki/Packet_processing" target="_blank">
+      <img
+        src="https://www.erg.abdn.ac.uk/users/gorry/course/images/ip-send.gif"
+        alt="schema packet processing"
+        width="400" 
+      />
+    </a>
+    <p>
+      The processing of any packet sent to a loopback address, is implemented in
+      the link layer of the TCP/IP stack. Such packets are never passed to any
+      network interface controller (NIC) or hardware device driver and must not
+      appear outside of a computing system, or be routed by any router. This
+      permits software testing and local services in the absence of any hardware
+      network interfaces. <br /><br />
+      Looped-back packets are distinguished from any other packets traversing
+      the TCP/IP stack only by the special IP address they were addressed to.
+      Thus, the services that ultimately receive them respond according to the
+      specified destination. For example, an HTTP service could route packets
+      addressed to <q>127.0.0.99:80</q> and 127.0.0.100:80 to different Web servers, or
+      to a single server that returns different web pages. To simplify such
+      testing, the hosts file may be configured to provide appropriate names for
+      each address.
+      <br /><br />
+      Packets received on a <u>non-loopback</u> interface with a loopback source or
+      destination address must be dropped. Such packets are sometimes referred
+      to as Martian packets.[6] As with any other bogus packets, they may be
+      malicious and <u>any problems</u> they might cause can be avoided by applying
+      bogon filtering.
+    </p>
+    <h2>Special cases</h2>
+
+    <p>
+      The releases of the
+      <a href="https://www.mysql.com/it/" target="_blank">MySQL</a> database
+      differentiate between the use of the hostname localhost and the use of the
+      addresses 127.0.0.1 and ::1.[7] <q>When</q> qusing localhost as the destination in
+      a client connector interface of an application, the MySQL application
+      programming interface connects to the database using a Unix domain socket,
+      while a TCP connection via the loopback interface requires the direct use
+      of the explicit address. <br /><br />
+      One notable exception to the use of the <u>127.0.0.0/8</u> addresses is their use
+      in Multiprotocol Label <q>Switching</q> (MPLS) traceroute error detection, in
+      which their property of not being routable provides a convenient means to
+      avoid delivery of faulty packets to end users.
+    </p>
+  </body>
+</html>
diff --git a/TPSI/costanzo_francesco/css/esercizio_css_19/ietf.jpeg b/TPSI/costanzo_francesco/css/esercizio_css_19/ietf.jpeg
diff --git a/TPSI/costanzo_francesco/css/esercizio_css_20/costanzo_esercizio_css_20.css b/TPSI/costanzo_francesco/css/esercizio_css_20/costanzo_esercizio_css_20.css
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+h1{
+    text-transform: uppercase;
+    color:blue;
+}
+
+h2{
+    text-transform: capitalize;
+    text-decoration: underline;
+    color:red;
+}
+
+p{
+    text-align: justify;
+
+}
+
+#p3{
+    text-align: right;
+}
+
+#obreggiatura{
+    text-shadow: 2px 2px 5px red;
+}