My set up is as follows:

OS: CentOS 6.2 running on an OpenVZ virtual machine.

Web server: Nginx listening on port 8080

Reverse proxy: Varnish listening on port 80

The problem is that Varnish redirects my requests to port 8080 and this appears in the address bar like so http://mysite.com:8080/directory/, causing relative links on the site to include the port number (8080) in the request and thus bypassing Varnish.

The site is powered by WordPress.

How do I allow Varnish to use Nginx as the backend on port 8080 without appending the port number to the address?

Edit: Varnish is set up like so:

I have told the Varnish daemon to listen to port 80 by default.

VARNISH_VCL_CONF=/etc/varnish/default.vcl
#
# # Default address and port to bind to
# # Blank address means all IPv4 and IPv6 interfaces, otherwise specify
# # a host name, an IPv4 dotted quad, or an IPv6 address in brackets.
# VARNISH_LISTEN_ADDRESS=
VARNISH_LISTEN_PORT=80
#
# # Telnet admin interface listen address and port
VARNISH_ADMIN_LISTEN_ADDRESS=127.0.0.1
VARNISH_ADMIN_LISTEN_PORT=6082
#
# # Shared secret file for admin interface
VARNISH_SECRET_FILE=/etc/varnish/secret
#
# # The minimum number of worker threads to start
VARNISH_MIN_THREADS=1
#
# # The Maximum number of worker threads to start
VARNISH_MAX_THREADS=1000
#
# # Idle timeout for worker threads
VARNISH_THREAD_TIMEOUT=120
#
# # Cache file location
VARNISH_STORAGE_FILE=/var/lib/varnish/varnish_storage.bin
#
# # Cache file size: in bytes, optionally using k / M / G / T suffix,
# # or in percentage of available disk space using the % suffix.
VARNISH_STORAGE_SIZE=1G
#
# # Backend storage specification
VARNISH_STORAGE="file,${VARNISH_STORAGE_FILE},${VARNISH_STORAGE_SIZE}"
#
# # Default TTL used when the backend does not specify one
VARNISH_TTL=120

The VCL file that Varnish calls (through an include in default.vcl) consists of:

backend playwithbits {
     .host = "127.0.0.1";
     .port = "8080";
}
acl purge {
     "127.0.0.1";
}
sub vcl_recv {
     if (req.http.Host ~ "^(.*\.)?playwithbits\.com$") {
          set req.backend = playwithbits;
          set req.http.Host = regsub(req.http.Host, ":[0-9]+", ""); 
          if (req.request == "PURGE") {
               if (!client.ip ~ purge) {
                    error 405 "Not allowed.";
               }
               return(lookup);
          }
          if (req.url ~ "^/$") {
               unset req.http.cookie;
          }
     }
}
sub vcl_hit {
     if (req.http.Host ~ "^(.*\.)?playwithbits\.com$") {
          if (req.request == "PURGE") {
               set obj.ttl = 0s;
                    error 200 "Purged.";
          }
     }
}
sub vcl_miss {
     if (req.http.Host ~ "^(.*\.)?playwithbits\.com$") {
          if (req.request == "PURGE") {
               error 404 "Not in cache.";
          } 
          if (!(req.url ~ "wp-(login|admin)")) {
               unset req.http.cookie;
          }
          if (req.url ~ "^/[^?]+.(jpeg|jpg|png|gif|ico|js|css|txt|gz|zip|lzma|bz2|tgz|tbz|html|htm)(\?.|)$") {
               unset req.http.cookie;
               set req.url = regsub(req.url, "\?.$", "");
          }
          if (req.url ~ "^/$") {
               unset req.http.cookie;
          }
     }
}
sub vcl_fetch {
     if (req.http.Host ~ "^(.*\.)?playwithbits\.com$") {
          if (req.url ~ "^/$") {
               unset beresp.http.set-cookie;
          }
          if (!(req.url ~ "wp-(login|admin)")) {
               unset beresp.http.set-cookie;
          }
     }
}