Nginx load balacing mono backend servers

guys i have tree web services running mono for asp.net

http://1.1.1.1:6789/Service.asmx
http://1.1.1.2:6789/Service.asmx
http://1.1.1.3:6789/Service.asmx
and i have this on my nginx web servers

upstream wsservices {
ip_hash;
server 1.1.1.1:6789;
server 1.1.1.2:6789;
server 1.1.1.3:6789;
}


server {
listen 8192;
error_page 502 503 504 @wsmant;
location / {
#proxy_set_header Host $host;
#proxy_set_header X-Real-IP $remote_addr;
#proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
#proxy_redirect off;
proxy_pass http://wsservices;
}
location @wsmant {
root /proxy/www;
rewrite ^(.*) /wsmant.html break;
}
}
i can acces to the ws from the nginx but when i hit invoke i get

http://wsservices:8080/Service.asmx/testconnection? net::ERR_NAME_NOT_RESOLVED
and the problem is???? thanks!