FTP java.net.ConnectException: Connection refused: connect
排查问题如下： 一般是端口写错引起的
（1）：利用linux命令查看端口 netstat -auntp | grep 21
Last login: Fri Oct 28 12:12:24 2016 from 116.226.185.223
[root@localhost ~]# netstat -auntp | grep 21
tcp 0 0 0.0.0.0:2121 0.0.0.0:* LISTEN 20143/vsftpd
tcp 0 0 :::3306 :::* LISTEN 2184/mysqld
tcp 0 0 ::ffff:127.0.0.1:3306 ::ffff:127.0.0.1:33699 ESTABLISHED 2184/mysqld
tcp 0 0 ::ffff:127.0.0.1:3306 ::ffff:127.0.0.1:33700 ESTABLISHED 2184/mysqld
tcp 0 0 ::ffff:127.0.0.1:3306 ::ffff:127.0.0.1:33661 ESTABLISHED 2184/mysqld
tcp 0 0 ::ffff:127.0.0.1:3306 ::ffff:127.0.0.1:33688 ESTABLISHED 2184/mysqld
tcp 0 0 ::ffff:127.0.0.1:3306 ::ffff:127.0.0.1:33625 ESTABLISHED 2184/mysqld
tcp 0 0 ::ffff:127.0.0.1:3306 ::ffff:127.0.0.1:33687 ESTABLISHED 2184/mysqld
tcp 0 0 ::ffff:127.0.0.1:3306 ::ffff:127.0.0.1:33702 ESTABLISHED 2184/mysqld
[root@localhost ~]# （2）: 如果连接后 读取数据为空 则 做如下修改：
ftp.enterLocalPassiveMode();//如果不加这个读取数据会为空
FTPFile[] fs = ftp.listFiles();
（3）：完整代码如下：
public void ReadFileFromSftp() {
String path="uploads//";
String fileName="20161012buy.txt";
String result="";
FTPClient ftp = new FTPClient();
try {
int reply;
//1.连接服务器
ftp.connect(server,2121);
//2.登录服务器 如果采用默认端口，可以使用ftp.connect(url)的方式直接连接FTP服务器
ftp.login(user, password);
//3.判断登陆是否成功
reply = ftp.getReplyCode();
if (!FTPReply.isPositiveCompletion(reply)) {
ftp.disconnect();
}
//4.指定要下载的目录
ftp.changeWorkingDirectory(path);// 转移到FTP服务器目录
//5.遍历下载的目录
ftp.enterLocalPassiveMode();
FTPFile[] fs = ftp.listFiles();
for (FTPFile ff : fs) {
//解决中文乱码问题，两次解码
byte[] bytes=ff.getName().getBytes("iso-8859-1");
String fn=new String(bytes,"utf8");
if (fn.equals(fileName)) {
InputStream inputStream=ftp.retrieveFileStream(ff.getName());
result = IOUtils.toString(inputStream);
}
}
ftp.logout();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (ftp.isConnected()) {
try {
ftp.disconnect();
} catch (IOException ioe) {
}
}
}
System.out.println("result"+result);
}
}
