TCP/IP connections

Max. new Connections per 5 seconds
This is the number of new connections eMule opens during 5 seconds. Default is 20.

Important:
>	Messing with this setting can cause blue screens, hung routers and the inability to browse the web. Also Up- and Download may suffer with wrong settings here.
>	You may slightly increase this setting when running eMule on high bandwidth connections like Tx or LAN.

Max. Half Open Connections
This setting became necessary with the connection throttling of Windows XP SP2. This update in XP will only allow 10 half open connections and then starts parking further connections in a queue which is only slowly processed. This leads to timeout and other undesired effects in eMule.
If eMule is running on XP SP2 do not set this value any higher than 9. Although there are patches to increase this hardcoded value in XP, it is not recommended to patch such critical parts in Windows. The only effect this setting does have is that eMule acquires sources a bit slower right after startup. This will subside after the sources have been found.
In other operating systems like Windows 2000 or the obsolete Windows 95/98/ME set this value to 50.

Fast connection reject
Fast Connection Reject uses a more efficient method to reject incoming TCP connection attempts of banned clients and/or from clients which IPs are found in IP-filter list. It's using a special Winsock feature called "conditional accept" which leads to less TCP overhead in case the TCP connection is rejected.

Server Connection Refresh Interval
There have been cases reported, that eMule loses the server connection in regular intervals when operating behind a router or network configurations which use NAT - Network Address Translation.
Routers often have a timeout for these NATed connections after which the router declares the connection for dead and closes it. When this happens and eMule tries to recheck its server, a full reconnect is needed because the old one has been removed by the router.
Should this issue occur, look up the value for the NAT timeout in your router's settings and enter a slightly lower value into the Server Connection Refresh Interval field. A value of 0 means eMule handles this and there is usually no need to change that!
Do not mess this this setting unless you have a router or a more complicated network setup. This may get you banned from the servers if the value is too low.

Use Credit System (Reward Uploaders)
See the chapter Credit System for more information first. It is strongly recommended to leave the Credit System turned on as it will deter leechers from harming the network.

Autotake eD2k Links only during runtime
This option only associates the eD2k link format when eMule is actually up. When eMule is closed the association is deleted to allow uninterrupted working of other eD2k clients.

Open/close ports on Win XP firewall when starting/exiting eMule
eMule is able to automatically open its needed ports in the internal Windows XP firewall. This setting will further increase security by not keeping the ports open after eMule is closed and to open them up again when it is started. This setting is only available in Windows XP and only for the internal firewall, not any third party products. This option is depricated for Windows versions newer than XP SP1.

Filter server and client LAN IPs
Sources containing IPs of the private IP classes A (10.0.0.0 - 10.255.255.255), B (172.16.0.0 - 172.31.255.255), C (192.168.0.0 - 192.168.255.255), local host (127.0.0.0 to 127.255.255.254) and all IPs starting with null (0.x.x.x) are not valid in the internet. Such sources received by client to client source exchange or by servers are dropped when this filter is activated.

Note:
Running eMule in a local network (LAN) requires this option be turned off or eMule will not be able to find any sources in this network.

Show more controls (advanced mode controls)
This options activates even more functions in eMule which are usually not needed for running it, but might be intresting and helpful for advanced users.

Disable automatic archive preview start in file details
When you check the file details for an archive eMule creates are preview to show you which files are within this archive. You can disable this behaviour to avoid having to wait (a short time on slow PCs) when walking through the file details. In this case you can still start the preview manually for each archive.

Disable A4AF checks to save CPU
This will turn off any source handling as described in the Advanced Source Handling chapter. Only when a download is canceled, potential A4AF sources are redistributed according to the priorities.

Hostname for own eD2k Links
In the shared files main tab eD2k links with the current IP as source can be created. Entering a hostname in this filed allows to create such links with the hostname instead of the IP. The advantage of this link is that it is still valid should your IP change.
For more information on dynamic hostnames see the Webinterface chapter.

Disable downloading from PeerCache
PeerCache is a system that will cache downloads in a completely anonymous way at the ISP level. This will decrease the amount of traffic an ISP has to cope with by buffering parts of downloads in its own system and so also providing better download speeds for the users. ISPs have to support this feature to be effective. Peercache is considered deprecated and disabled by default.

Create new part files as sparse (NTFS only)
Sparse files are an NTFS (NT File System) feature, thus only available when the harddisk is formatted using NTFS.
As the single parts or chunks of a file are not necessarily downloaded in the correct sequence, the space between the already-downloaded parts are filled with zeros. Usually these zeros would eat up space on the harddisk the same way as if they were actually filled with useful data. To prevent this the NTFS sparse file support does not store the zeros but keeps track of where the single parts actually belong in the file. This reduces the diskspace overhead needed during a download. When the file is finished NTFS takes care of the correct sequence of all the parts.
Due to a bug in Windows, sparse files are currently disabled on Windows Vista and later version.

Allocate full file size on non-sparse part files
By default eMule allocates just as much space on your diskdrive for a while, which is necessary to write the received data to its proper position. By using this option, eMule allocates space for the complete file on the first write which can reduce disk fragmentation but might use up more space than needed at a given point. This option is ignored for sparse files.

Check Diskspace (min. free diskspace [MB])
The size of eMule's temporary download files increases dynamically on demand. The Check Diskspace option ensures that the current downloads can be entirely downloaded and completed. Downloads which are too big for the current free disk space get paused so that other downloads can be completed.
If you provide a value for the min. free diskspace eMule's behavior changes. Now all files are downloaded until the limit for free disk space is reached.
When free disk space increases the paused downloads will restart automatically.

Safe .met / .dat file writing
On newer operating systems using NTFS as file system there is usually no need to change this option. If downloads are reproducibly lost on crashes or eMule shut downs the safer method should be tried.
Depending on the hardware used, this option may notably increase disk activity / system load or prolong eMule's shut down!

• Never
  eMule will never use extra safety measures to commit the .met and .dat files to disk on application exit.
• On shutdown
  eMule will use extra safety measures to commit the .met and .dat files to disk on application exit. This may prolong the time needed for shut down.
• Always
  The safety measures are used on every write access to these files.

Extract meta data
This feature controls how meta data (bitrate, resolution, codec etc) is extracted from finished/newly hashed files. This data is then published to servers or the Kademlia network. In the search options it can be specified e.g. to search only for mp3 files with a bitrate of at least 128 kb/s.

• Never
  The meta data is never extracted
• ID3 Library
  ID3 Library, a third party dll, is used to extract the meta data. This only works for *.mp1, *.mp2, *.mp3 and *.mpa files. To use it the windows binaries of this library have to be downloaded and put into eMule's installation folder.

Resolve shell links in shared directories
If this option is enabled, eMule will follow shell links found in shared directories and share the source file, even if the source file is not in a shared directory itself. eMule handles the shell link in this case as if it was the source file itself, however you will not be able to single unshare or single share a shell link.

Save logs to disk
The output of the two log windows of the Server tab - Log and Debug - can be saved to disk by turning on the corresponding option. They will be save as eMule.log or eMule_Debug.log in eMule's installation folder.

Verbose (additional program feedback)
If Verbose mode is turned on an additional Debug tab is displayed in the Server window. The information shown therein are for development only and no additional support on these will be provided. This option causes a greater CPU and memory load. Not recommended for normal operation.
The Log Level option controls which log messages are shown. Level 5 means all verbose messages whereas level 1 shows only the most important one. If you want to know the importance the various messages have look it up in eMule's source code ;)

Upload Speed Sense (USS)
USS is a function to monitor the ping times of the connection and to automatically adjust eMule's upload according to this ping value. This ensures that the connection never cloggs and will try to keep surfing and online gaming fluid. It is recommended to keep the default settings.

Please note: It is recommended to set an upload limit in the connection preferences even if USS is enabled. USS will respect the manually set upload limit and never go above that, and knowing the absolute max will help it reach a more stable upload speed.

Find best upload limit automatically
Activates USS

Lowest allowed upload speed
This is the minimum upload USS must keep. Recommended is at least 50% of your upload capacity

Ping Tolerance (% of lowest ping)
A initial average ping is determined for the connection when eMule starts. USS will not allow a ping increase over the initial ping times the entered multiplier, e.g. an initial ping of 50 ms and 800% ping tolerance will result in a maintained maximum ping of 400 ms.

Ping Tolerance (ms)
Instead of calculating the maximum allowed ping by a % modifier also a value in milliseconds can be specified. See next setting.

Method for ping tolerance
Chooses the preferred method for determining the maximum allowed ping. Either the percentage or the millisecond modifier is used.

Going up / down slowness
These two values describe how fast the upload limit is adjusted to stay within the ping tolerance. Setting wrong values here will collapse the connection. Keep default!

Maximum number of pings for average
Sets the number of pings needed to calculate the average response time.

UPnP

Remove UPnP port forwardings on exit
If you enabled UPnP, eMule will forward or open the necessary ports on start up in order to be reachable for other users. By default it will try to remove those forwardings (close those ports) once you close eMule, because they are no longer needed. If you do not want eMule to remove those forwardings for some reason, you can disable this behaviour by unchecking this option.

Sharing eMule with other computer users
This option allows you to change how eMule should behave on a multi-user system. The main difference is that either all users have the same downloads and settings or each user has its own. You can read here more about this feature.
It is important to notice that if you change this setting, eMule will use another directory for its configuration files, which will result in a "loss" of all settings. This means you will also not see your downloads or shared files, because eMule is using different default directories. But of course you can always adjust them in the directory dialog. You can also always revert this option and all your old setting will be still there.
You need to restart eMule if you change this option to see any effect.

File Buffer Size
Some system may display a "stuttering" when eMule flushes its file buffers. Lowering the buffer size may help in this case but will result in a higher disk activity caused by eMule as data is written to disk more frequently. Setting the buffer size too low can severely reduce eMule's performance.
Increasing the buffer will reduce disk activity but at the risk of higher data loss should problems occur.

Queue Size
For the Credit System in eMule to work properly the queue size is very important. If a client has a full queue another client with a high credit rating will have no chance to enter the queue to spend his credits. So the larger the queue is, the better and smoother credit system will work. Clients with high credits will advance in long queues fast enough to get their share. Also, queue waiting time is not reduced when reconnecting due to IP change or similar. Time until reconnected may not exceed 1 hour or the queue position will be lost.

Important:
A larger queue does not result in a larger overhead for managing this queue. Neither the number of connections nor the connection overhead will be increased by a larger queue. Larger queues may use more memory.