CASE 4 is similar to CASE 3 but it always uses the same destination IP address:
In this example "102.10.0.0".

When sending: (0x2)abcdef 

bash-2.04# strace -f reverse/the-binary4
execve("reverse/the-binary4", ["reverse/the-binary4"], [/* 35 vars */]) = 0
personality(PER_LINUX)                  = 0
geteuid()                               = 0
sigaction(SIGCHLD, {SIG_IGN}, {SIG_DFL}, 0x4006b008) = 0
setsid()                                = 1651
sigaction(SIGCHLD, {SIG_IGN}, {SIG_IGN}, 0x80575a8) = 0
chdir("/")                              = 0
close(0)                                = 0
close(1)                                = 0
close(2)                                = 0
time(NULL)                              = 1022196221
socket(PF_INET, SOCK_RAW, 0xb /* IPPROTO_??? */) = 0
sigaction(SIGHUP, {SIG_IGN}, {SIG_DFL}, 0x4006b008) = 0
sigaction(SIGTERM, {SIG_IGN}, {SIG_DFL}, 0x4006b008) = 0
sigaction(SIGCHLD, {SIG_IGN}, {SIG_IGN}, 0x80575a8) = 0
sigaction(SIGCHLD, {SIG_IGN}, {SIG_IGN}, 0x80575a8) = 0
recv(0, "E\0\5\334\26\301@\0@\v\231\370\300\250\1\17\300\250\1\376"..., 2048, 0) = 1500

socket(PF_INET, SOCK_RAW, IPPROTO_RAW)  = 1
sendto(1, "E\0(\34\4U\37\376\234\21lt\0\0\0\0f\n\0\0\0\30\0e\0\t\377"..., 29, 0, {sin_family=AF_INET, sin_port=htons(222), sin_addr=inet_addr("102.10.0.0")}}, 16) = -1 ENETUNREACH (Network is unreachable)
sendto(1, "E\0(\34\4U\37\376\234\21lt\0\0\0\0f\n\0\0\0\30\0e\0\t\377"..., 29, 0, {sin_family=AF_INET, sin_port=htons(222), sin_addr=inet_addr("102.10.0.0")}}, 16) = -1 ENETUNREACH (Network is unreachable)
oldselect(1, NULL, NULL, NULL, {0, 20}) = 0 (Timeout)
sendto(1, "E\0(\34\4U\37\376\234\21lt\0\0\0\0f\n\0\0\0\30\0e\0\t\377"..., 29, 0, {sin_family=AF_INET, sin_port=htons(222), sin_addr=inet_addr("102.10.0.0")}}, 16) = -1 ENETUNREACH (Network is unreachable)
sendto(1, "E\0(\34\4U\37\376\234\21lt\0\0\0\0f\n\0\0\0\30\0e\0\t\377"..., 29, 0, {sin_family=AF_INET, sin_port=htons(222), sin_addr=inet_addr("102.10.0.0")}}, 16) = -1 ENETUNREACH (Network is unreachable)
oldselect(1, NULL, NULL, NULL, {0, 20}) = 0 (Timeout)
sendto(1, "E\0(\34\4U\37\376\234\21lt\0\0\0\0f\n\0\0\0\30\0e\0\t\377"..., 29, 0, {sin_family=AF_INET, sin_port=htons(222), sin_addr=inet_addr("102.10.0.0")}}, 16) = -1 ENETUNREACH (Network is unreachable)
sendto(1, "E\0(\34\4U\37\376\234\21lt\0\0\0\0f\n\0\0\0\30\0e\0\t\377"..., 29, 0, {sin_family=AF_INET, sin_port=htons(222), sin_addr=inet_addr("102.10.0.0")}}, 16) = -1 ENETUNREACH (Network is unreachable)
oldselect(1, NULL, NULL, NULL, {0, 20}) = 0 (Timeout)
sendto(1, "E\0(\34\4U\37\376\234\21lt\0\0\0\0f\n\0\0\0\30\0e\0\t\377"..., 29, 0, {sin_family=AF_INET, sin_port=htons(222), sin_addr=inet_addr("102.10.0.0")}}, 16) = -1 ENETUNREACH (Network is unreachable)

...


If you send a different data information: (0x2)abcfedghi , you get a different destination address, so you can select it
based on the data input:
sendto(1, "E\0(\34\4U\37\376\222\21\5\256\n\0\0\0dghi\0\213\0e\0\t"..., 29, 0, {sin_family=AF_INET, sin_port=htons(174), sin_addr=inet_addr("100.103.104.105")}}, 16) = -1 ENETUNREACH (Network is unreachable)  

The destination IP address is not based in the data input leght but in the information sent, the contents.


Some examples showing how the destination IP address changes based on the data input:

(0x2)abcd   

sendto(1, "E\0(\34\4U\37\376\224\21\332~\0\0\0\0\0\0\0\0\0\236\0\n"..., 29, 0,
{sin_family=AF_INET, sin_port=htons(165), sin_addr=inet_addr("0.0.0.0")}}, 16)
= 29 

(0x2)abcde 

sendto(1, "E\0(\34\4U\37\376\221\21\323~\0\0\0\0\n\0\0\0\0-\0e\0\t"..., 29, 0,
{sin_family=AF_INET, sin_port=htons(119), sin_addr=inet_addr("10.0.0.0")}},
16) = 29

(0x2)abcdef 

sendto(1, "E\0(\34\4U\37\376\342\21&t\0\0\0\0f\n\0\0\0F\0e\0\t\377"..., 29, 0,
{sin_family=AF_INET, sin_port=htons(182), sin_addr=inet_addr("102.10.0.0")}},
16) = 29  


As can be seen, the 5th byte sent (for example, in "abcde", the "e"), is the first element taken to 
build the destination IP address. But it just forces a "10" value in the address. The next char is 
the following octect in the IP address and so on:

(0x2)abcdefg 

sendto(1, "E\0(\34\4U\37\376\207\21w\27\0\0\0\0fg\n\0\0I\0e\0\t\377"..., 29,
0, {sin_family=AF_INET, sin_port=htons(26),
sin_addr=inet_addr("102.103.10.0")}}, 16) = 29 


(0x2)abcdefgh 

sendto(1, "E\0(\34\4U\37\376\203\21\35\r\0\0\0\0fgh\n\0\372\0e\0\t"..., 29, 0,
{sin_family=AF_INET, sin_port=htons(120),
sin_addr=inet_addr("102.103.104.10")}}, 16) = 29 


(0x2)abcdefghi 

sendto(1, "E\0(\34\4U\37\376\323\21\302\255\n\0\0\0fghi\0\363\0e\0"..., 29, 0,
{sin_family=AF_INET, sin_port=htons(174),
sin_addr=inet_addr("102.103.104.105")}}, 16) = 29


(0x2)abcdefghij 

sendto(1, "E\0(\34\4U\37\376\244\21\221\243j\n\0\0fghi\0005\0e\0\t"..., 29, 0,
{sin_family=AF_INET, sin_port=htons(192),
sin_addr=inet_addr("102.103.104.105")}}, 16) = 29


Its the same as the previous one, so only the 4 bytes 6,7,8,9 define the destination IP address.
If you miss some of the characters, it places a "10" value instead, followed by "0" values.