diff --git a/Cargo.toml b/Cargo.toml
index e88eb3ff5a529bd8b4454f1424f3529fdb99c0fa..975f1ac041e56bc71a3e2953ddc939500b43ebfc 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -18,13 +18,15 @@ serde = { version = "1.0.114", features = ["derive"] }
 getrandom = "0.1.14" # tiny crate. used to guess controller-id
 
 # network
-# integer-encoding = "1.1.5"
-# byteorder = "1.3.4"
 mio = { version = "0.7.0", package = "mio", features = ["udp", "tcp", "os-poll"] }
 
 # protocol
 backtrace = "0.3"
 
+# socket ffi
+lazy_static = { version = "1.4.0", optional = true}
+atomic_refcell = { version = "0.1.6", optional = true }
+
 [dev-dependencies]
 # test-generator = "0.3.0"
 crossbeam-utils = "0.7.2"
@@ -36,6 +38,7 @@ crate-type = ["cdylib"]
 
 [features]
 default = ["ffi", "session_optimization"]
-ffi = [] # no feature dependencies
+ffi = [] # see src/ffi.rs
+ffi_socket_api = ["ffi", "lazy_static", "atomic_refcell"]
 endpoint_logging = [] # see src/macros.rs
 session_optimization = [] # see src/runtime/setup.rs
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