how to use proxy_bind

Dears,

I test has three servers.

1.client server 2.nginx server 3.server server

my nginx configure like as below:

worker_processes  2;
#error_log  logs/error.log;
#error_log  logs/error.log  notice;
#error_log  logs/error.log  info;
#pid        logs/nginx.pid;
events {
    worker_connections  1024;

}
stream {
upstream a{
server 192.168.14.139:10000;
}

upstream b{
server 192.168.14.139:10001;
}

server {

listen 10000 udp;
proxy_pass a;
proxy_timeout 1s;
proxy_responses 1;
error_log logs/a.log;
}

server {
listen 10001 udp;
proxy_pass b;
proxy_timeout 1s;
proxy_responses 1;
error_log logs/b.log;
}
}

But i found like as below

1.if client use 11111 to connect nginx server

2.nginx server will use new port to connect server server the port will changed to 11112

3.i wanted client use 11111 -> nginx ,nginx also use 11111 to connect server to keep the session.

i found some answer they says can use: proxy_bind $remote_addr transparent;

but i add as below:

server {
listen 10001 udp;
proxy_pass b;
proxy_timeout 1s;
proxy_responses 1;
proxy_bind $remote_addr transparent;
error_log logs/a.log;
}

its return error: nginx: [emerg] invalid number of arguments in "proxy_bind"