Proftpd默默地失败。 系统说它正在运行，但它不接受连接

我已经在Centos 7机器上安装了proftpd 。

这是systemctl -l status proftpd的输出：

 proftpd.service - ProFTPD FTP Server Loaded: loaded (/usr/lib/systemd/system/proftpd.service; enabled; vendor preset: disabled) Active: active (running) since gio 2017-06-15 08:46:23 EDT; 2s ago Process: 5358 ExecStart=/usr/sbin/proftpd $PROFTPD_OPTIONS (code=exited, status=0/SUCCESS) Main PID: 5359 (proftpd) CGroup: /system.slice/proftpd.service └─5359 proftpd: (accepting connections giu 15 08:46:23 edmure.francescoruvolo.com systemd[1]: Starting ProFTPD FTP Server... giu 15 08:46:23 edmure.francescoruvolo.com proftpd[5359]: 64.137.242.120 - ProFTPD 1.3.5e (maint) (built Wed May 3 2017 14:58:47 UTC) standalone mode STARTUP giu 15 08:46:23 edmure.francescoruvolo.com systemd[1]: Started ProFTPD FTP Server. 

所有的start ， stop和restart命令都能正常工作，不会显示任何错误。

我用--testconfig检查了configuration，并没有显示任何错误。 无论如何，这里是完整的proftpd.conf文件，虽然我没有改变任何选项，所以很奇怪，它不是开箱即用。

• 虚拟主机与proftpd的问题
• proftpd审计错误
• Proftpd：在接收地图结构时，使用filezillalogin失败
• Proftpd用户身份validation与mod_sql / mod_sql_passwd
• Proftpd正在运行，但无法通过FileZillabuild立连接

/var/log/proftpd/中没有日志。 /var/log/messages/只显示与systemctl status相同的行。

没有防火墙规则：

 Chain INPUT (policy ACCEPT) target prot opt source destination Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination 

不过，我无法使用netcat来连接端口21，甚至从本地主机。 和netstat -tulpn | grep :21 netstat -tulpn | grep :21不显示任何输出。

这是proftpd -V的输出：

 Compile-time Settings: Version: 1.3.5e (maint) Platform: LINUX [Linux 3.10.0-514.21.1.el7.x86_64 x86_64] Built: Wed May 3 2017 14:58:47 UTC Built With: configure '--build=x86_64-redhat-linux-gnu' '--host=x86_64-redhat-linux-gnu' '--program-prefix=' '--disable-dependency-tracking' '--prefix=/usr' '--exec-prefix=/usr' '--bindir=/usr/bin' '--sbindir=/usr/sbin' '--sysconfdir=/etc' '--datadir=/usr/share' '--includedir=/usr/include' '--libdir=/usr/lib64' '--libexecdir=/usr/libexec' '--localstatedir=/var' '--sharedstatedir=/var/lib' '--mandir=/usr/share/man' '--infodir=/usr/share/info' '--libexecdir=/usr/libexec/proftpd' '--localstatedir=/run/proftpd' '--disable-strip' '--enable-ctrls' '--enable-dso' '--enable-facl' '--enable-ipv6' '--enable-memcache' '--enable-nls' '--enable-openssl' '--enable-pcre' '--enable-shadow' '--enable-tests' '--with-libraries=/usr/lib64/mysql' '--with-includes=/usr/include/mysql' '--with-modules=mod_readme:mod_auth_pam:mod_tls' '--with-shared=mod_sql:mod_sql_passwd:mod_sql_mysql:mod_sql_postgres:mod_quotatab:mod_quotatab_file:mod_quotatab_ldap:mod_quotatab_radius:mod_quotatab_sql:mod_ldap:mod_ban:mod_wrap:mod_ctrls_admin:mod_facl:mod_load:mod_vroot:mod_radius:mod_ratio:mod_rewrite:mod_site_misc:mod_exec:mod_shaper:mod_geoip:mod_wrap2:mod_wrap2_file:mod_wrap2_sql:mod_copy:mod_deflate:mod_ifversion:mod_qos:mod_sftp:mod_sftp_pam:mod_sftp_sql:mod_tls_shmcache:mod_tls_memcache:mod_ifsession' 'build_alias=x86_64-redhat-linux-gnu' 'host_alias=x86_64-redhat-linux-gnu' 'CFLAGS=-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -m64 -mtune=generic' 'LDFLAGS=-Wl,-z,relro -specs=/usr/lib/rpm/redhat/redhat-hardened-ld' 'CXXFLAGS=-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -m64 -mtune=generic' CFLAGS: -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -m64 -mtune=generic -Wall LDFLAGS: -L$(top_srcdir)/lib -Wl,-z,relro -specs=/usr/lib/rpm/redhat/redhat-hardened-ld -L/usr/lib64/mysql -L/usr/lib64/mysql -L/usr/lib64 LIBS: -lacl -lpcreposix -lpcre -lssl -lcrypto -lssl -lcrypto -lcap -lmemcached -lmemcachedutil -lssl -lcrypto -lpam -lsupp -lcrypt -ldl Files: Configuration File: /etc/proftpd.conf Pid File: /run/proftpd/proftpd.pid Scoreboard File: /run/proftpd/proftpd.scoreboard Header Directory: /usr/include/proftpd Shared Module Directory: /usr/libexec/proftpd Features: - Autoshadow support + Controls support + curses support - Developer support + DSO support + IPv6 support + Largefile support - Lastlog support + Memcache support + ncursesw support + NLS support + OpenSSL support (FIPS enabled) + PCRE support + POSIX ACL support + Shadow file support + Sendfile support + Trace support Tunable Options: PR_TUNABLE_BUFFER_SIZE = 1024 PR_TUNABLE_DEFAULT_RCVBUFSZ = 8192 PR_TUNABLE_DEFAULT_SNDBUFSZ = 8192 PR_TUNABLE_GLOBBING_MAX_MATCHES = 100000 PR_TUNABLE_GLOBBING_MAX_RECURSION = 8 PR_TUNABLE_HASH_TABLE_SIZE = 40 PR_TUNABLE_NEW_POOL_SIZE = 512 PR_TUNABLE_SCOREBOARD_BUFFER_SIZE = 80 PR_TUNABLE_SCOREBOARD_SCRUB_TIMER = 30 PR_TUNABLE_SELECT_TIMEOUT = 30 PR_TUNABLE_TIMEOUTIDENT = 10 PR_TUNABLE_TIMEOUTIDLE = 600 PR_TUNABLE_TIMEOUTLINGER = 30 PR_TUNABLE_TIMEOUTLOGIN = 300 PR_TUNABLE_TIMEOUTNOXFER = 300 PR_TUNABLE_TIMEOUTSTALLED = 3600 PR_TUNABLE_XFER_SCOREBOARD_UPDATES = 10 

我迷路了，不知道如何进一步解决问题。 我也删除并重新安装了该软件包，但没有任何改变。