在路由器后,使用filezilla通过active mode连接ftp服务器,有时会遇到经常断线的问题.为什么说”有时”,因为连其中一台服务器正常不断线,连另一台就时常断线,所以许久没找到原因.
今天去filezilla官网看了一下说明,才发现我可能犯了一个错误. 给filezilla限定的port range太窄了,以至于同时传送很多文件时,新的tcp连接没有端口可以使用.
所以,如果你也有相同的困扰,那就把防火墙可允许的port范围调大一点,当然了ftp server的连接数限制不用改变.
同理,如果使用pasv mode,ftp server允许的port range也要大大于连接数限制. 使得传送另一个文件时,有端口可用.
Valid ports can be from 1 to 65535; however, ports less than 1024 are reserved for other protocols. It is best to choose ports greater than or equal to 50000 for active mode FTP. Due to the nature of TCP (the underlying transport protocol), a port cannot be reused immediately after each connection. Therefore, the range of ports should not be too small to prevent the failure of transfers of multiple small files. A range of 50 ports should be sufficient in most cases.