[#SSL_CTX_set_alpn_protos]
= SSL_CTX_set_alpn_protos
:mrdocs:

Set the ALPN protocol list advertised or offered by an SSL context.

== Synopsis

Declared in `<openssl/ssl.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
SSL_CTX_set_alpn_protos(
    xref:SSL_CTX.adoc[SSL_CTX]* ctx,
    unsigned char const* protos,
    unsigned int protos_len);
----

== Return Value

0 on success, or non‐zero on failure (inverted success convention).

== Parameters

[cols="1,4"]
|===
| Name| Description
| *ctx*
| SSL context to configure.
| *protos*
| Wire‐format protocol list (length‐prefixed names); empty clears ALPN.
| *protos_len*
| Length of `protos` in bytes.
|===


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