JAVA /连接超时与套接字绑定

Question

Two parts:

  InetAddress ia = Inet4Address.getByAddress(new byte[]{(byte)192,(byte)168,(byte)10,(byte)100});
  Socket socket = new Socket();
  InetSocketAddress isa = new InetSocketAddress("82.146.58.81", 5277);
  socket.bind(new InetSocketAddress(ia, 0));
  System.out.println("local_address:" + socket.getLocalSocketAddress());
  socket.connect(isa, 1000);
  Thread.sleep(1000);
  socket.close();
  System.out.println("done_1");

  InetAddress ia_2 = Inet4Address.getByAddress(new byte[]{(byte)172,(byte)20,(byte)10,(byte)2});
  Socket socket_2 = new Socket();
  InetSocketAddress isa2 = new InetSocketAddress("82.146.58.81", 5277);
  socket_2.bind(new InetSocketAddress(ia_2, 0));
  System.out.println("local_address:" + socket_2.getLocalSocketAddress());
  socket_2.connect(isa2, 30000);
  Thread.sleep(1000);
  socket_2.close();
  System.out.println("done_2");

First part of code worked, second not - java.net.SocketTimeoutException: connect timed out. I am trying to communicate with the host "82.146.58.81" through different interfaces. But only the part that has the default route is successful. Why?

Update: I am worked by Ubuntu 17.10, seems the same problem in Armbian too. Problem not reproducible under Windows7

Update: Wrong OUT interface: [12979.049742] IN= OUT=enp4s0 SRC=172.20.10.2 DST=82.146.58.81 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=25967 DF PROTO=TCP SPT=48985 DPT=5277 WINDOW=29200 RES=0x00 SYN URGP=0

kostas@work:~$ ifconfig 
enp0s16f0u1c4i2: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.20.10.2  netmask 255.255.255.240  broadcast 172.20.10.15
        inet6 fe80::17c7:4582:897b:11d5  prefixlen 64  scopeid 0x20<link>
        ether 86:38:35:c8:f5:39  txqueuelen 1000  (Ethernet)
        RX packets 575  bytes 117085 (117.0 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 686  bytes 82681 (82.6 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

enp4s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.10.100  netmask 255.255.255.0  broadcast 192.168.10.255
        inet6 fe80::80b9:8cf3:92c6:4aef  prefixlen 64  scopeid 0x20<link>
        ether 00:e0:66:ae:2a:de  txqueuelen 1000  (Ethernet)
        RX packets 100455  bytes 65543315 (65.5 MB)
        RX errors 0  dropped 1  overruns 0  frame 0
        TX packets 75513  bytes 15658830 (15.6 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

kostas@work:~$ route
Таблица маршутизации ядра протокола IP
Destination Gateway Genmask Flags Metric Ref Use Iface
default         unknown         0.0.0.0         UG    100    0        0 enp4s0
default         gateway         0.0.0.0         UG    101    0        0 enp0s16f0u1c4i2


kostas@work:~$ ping mail.ru -I enp0s16f0u1c4i2
PING mail.ru (217.69.139.202) from 172.20.10.2 enp0s16f0u1c4i2: 56(84) bytes of data.
64 bytes from mail.ru (217.69.139.202): icmp_seq=1 ttl=51 time=508 ms
64 bytes from mail.ru (217.69.139.202): icmp_seq=2 ttl=51 time=187 ms

Answer 1

"However, many OSes do not honour this "hint" and will use the routing table anyway."

Answer here