---
name: "Tss2_Tcti_Mssim_Init"
section: "3"
platform: "linux"
package: "tpm2-tss"
version: "4.2.0-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/Tss2_Tcti_Mssim_Init"
---

# Tss2\_Tcti\_Mssim\_Init(3)

Initialization function for the Microsoft TPM simulator TCTI library.

## NAME

Tss2\_Tcti\_Mssim\_Init - Initialization function for the Microsoft TPM simulator TCTI library.

## SYNOPSIS

**#include \<tcti/tcti\_mssim.h\>**

**TSS2\_RC Tss2\_Tcti\_Mssim\_Init (TSS2\_TCTI\_CONTEXT** *\*tctiContext***, size\_t** *\*contextSize***, const char** *\*conf***);**

The **Tss2\_Tcti\_Mssim\_Init**() function initializes a TCTI context used to communicate with the Microsoft TPM2 simulator.

## DESCRIPTION

**Tss2\_Tcti\_Mssim\_Init**() attempts to initialize a caller allocated *tcti\_context* of size *size* using caller provided configuration string *conf* . Since the *tcti\_context* must be a caller allocated buffer, the caller needs to know the buffer size required by the TCTI library. The minimum size of this context can be discovered by providing **NULL** for the *tcti\_context* and a non- **NULL** *size* parameter. The initialization function will then populate the *size* parameter with the minimum size of the *tcti\_context* buffer. The caller must then allocate a buffer of this size (or larger) and call **Tss2\_Tcti\_Mssim\_Init ()** again providing the newly allocated *tcti\_context* and the size of this context in the *size* parameter. This pattern is common to all TCTI initialization functions. We provide an example of this pattern using the **Tss2\_Tcti\_Mssim\_Init**() function in the section titled **EXAMPLE.**

The *conf* parameter is a C string used to configure the TCTI context. This configuration string is a series of key / value pairs that specify the host and port used to connect to an instance of the Microsoft TPM2 simulator. The keys and values are separated by the '=' character, while each key / value pair is separated by the ',' character.

The only keys supported in the *conf* string are **host** and **port.** The host may be an IPv4 address, an IPv6 address, or a host name. The port must be a valid uint16\_t in string form. If a NULL *conf* string is provided by the caller then the default of "host=localhost,port=2321" is used. If either **host** or **port** are omitted then their respective default value will be used.

Once initialized, the TCTI context returned exposes the Trusted Computing Group (TCG) defined API for the lowest level communication with the TPM. Using this API the caller can exchange (send / receive) TPM2 command and response buffers with the Microsoft TPM simulator. In nearly all cases however, the caller will initialize a context using this function before passing the context to a higher level API like the System API (SAPI), and then never touch it again.

For a more thorough discussion of the TCTI API see the “TSS System Level API and TPM Command Transmission Interface Specification” as published by the TCG: https://trustedcomputinggroup.org/tss-system-level-api-tpm-command-transmission-interface-specification/

## RETURN VALUE

A successful call to **Tss2\_Tcti\_Mssim\_Init**() will return **TSS2\_RC\_SUCCESS.** An unsuccessful call will produce a response code described in section **ERRORS.**

## ERRORS

**TSS2\_TCTI\_RC\_BAD\_VALUE** is returned if both the *tcti\_context* and the *size* parameters are NULL, or if the *config* parameter is NULL.

## EXAMPLE

TCTI initialization fragment:

```
#include <inttypes.h>
#include <stdlib.h>
#include <stdio.h>
#include <tcti/tcti_mssim.h>
TSS2_RC rc;
TSS2_TCTI_CONTEXT *tcti_context;
size_t size;
const char *conf = "host=localhost,port=2321"
rc = Tss2_Tcti_Mssim_Init (NULL, &size, NULL);
if (rc != TSS2_RC_SUCCESS) {
    fprintf (stderr, "Failed to get allocation size for mssim TCTI "
             " context: 0x%" PRIx32 "0, rc);
    exit (EXIT_FAILURE);
}
tcti_context = calloc (1, size);
if (tcti_context == NULL) {
    fprintf (stderr, "Allocation for TCTI context failed: %s0,
             strerror (errno));
    exit (EXIT_FAILURE);
}
rc = Tss2_Tcti_Mssim_Init (&tcti_context, &size, conf);
if (rc != TSS2_RC_SUCCESS) {
    fprintf (stderr, "Failed to initialize mssim TCTI context: "
             "0x%" PRIx32 "0, rc);
    free (tcti_context);
    exit (EXIT_FAILURE);
}
```

## AUTHOR

TPM2 Software Project \<https://github.com/tpm2-software/tpm2-tss\>

## SEE ALSO

[**Tss2\_Tcti\_Device\_Init**(3)](/Tss2_Tcti_Device_Init/3.md), **Tss2\_Tcti\_Socket\_Init**(3), [**Tss2\_TctiLdr\_Initialize**(3)](/Tss2_TctiLdr_Initialize/3.md), [**Tss2\_TctiLdr\_Finalize**(3)](/Tss2_TctiLdr_Finalize/3.md), **tcti-device**(7), **tcti-socket**(7), **tcti-tabrmd**(7), [**tpm2-abrmd**(8)](/tpm2-abrmd/8.md)

## COLOPHON

This page is part of release 4.2.0 of Open Source implementation of the TCG TPM2 Software Stack (TSS2). A description of the project, information about reporting bugs, and the latest version of this page can be found at https://github.com/tpm2-software/tpm2-tss/.

## LICENSE

This work is licensed under the Creative Commons Attribution 4.0 International License (CC BY 4.0). For more information visit https://creativecommons.org/licenses/by/4.0/