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| ubuntu:ftp:active_vs_passive_ftp [2019/11/29 13:41] – created peter | ubuntu:ftp:active_vs_passive_ftp [2020/07/15 09:30] (current) – external edit 127.0.0.1 |
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| When drawn out, the connection appears as follows: | When drawn out, the connection appears as follows: |
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| {{:ftp:activeftp.gif|}} | {{:ftp:activeftp.gif?600|}} |
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| In step 1, the client's command port contacts the server's command port and sends the command PORT 1027. The server then sends an ACK back to the client's command port in step 2. In step 3 the server initiates a connection on its local data port to the data port the client specified earlier. Finally, the client sends an ACK back as shown in step 4. | In step 1, the client's command port contacts the server's command port and sends the command PORT 1027. The server then sends an ACK back to the client's command port in step 2. In step 3 the server initiates a connection on its local data port to the data port the client specified earlier. Finally, the client sends an ACK back as shown in step 4. |
| The main problem with active mode FTP actually falls on the client side. The FTP client doesn't make the actual connection to the data port of the server--it simply tells the server what port it is listening on and the server connects back to the specified port on the client. From the client side firewall this appears to be an outside system initiating a connection to an internal client--something that is usually blocked. | The main problem with active mode FTP actually falls on the client side. The FTP client doesn't make the actual connection to the data port of the server--it simply tells the server what port it is listening on and the server connects back to the specified port on the client. From the client side firewall this appears to be an outside system initiating a connection to an internal client--something that is usually blocked. |
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| ==== Active FTP Example ==== | ==== Active FTP Example ==== |
| 221 Goodbye. | 221 Goodbye. |
| </code> | </code> |
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| ===== Passive FTP ===== | ===== Passive FTP ===== |
| When drawn, a passive mode FTP connection looks like this: | When drawn, a passive mode FTP connection looks like this: |
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| {{:ftp:passiveftp.gif|}} | {{:ftp:passiveftp.gif?600|}} |
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| With the massive popularity of the World Wide Web, many people prefer to use their web browser as an FTP client. Most browsers only support passive mode when accessing <nowiki>ftp://</nowiki> URLs. This can either be good or bad depending on what the servers and firewalls are configured to support. | With the massive popularity of the World Wide Web, many people prefer to use their web browser as an FTP client. Most browsers only support passive mode when accessing <nowiki>ftp://</nowiki> URLs. This can either be good or bad depending on what the servers and firewalls are configured to support. |
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| ==== Passive FTP Example ==== | ==== Passive FTP Example ==== |
