As eyoung says, You need FTP Client and A text Editor.
You can use FileZilla and set it's editor on your prefered Editor, like Komodo, Kate, Gedit or etc through this URI:
Edit menu -> Settings -> File editing
Then when you connect to your ftp server you can just right click on file and choose edit. After you change the file and click save in your editor, Go to FileZille, FileZilla automatically detects the change and asks you if you want to replace the file to the server.
Also, some ftp clients like Konqueror witch is a global browser, will upload the file without question and shows the ftp directory like a local directory.