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I want to create a shared database c# windows form application?

This application that i am trying to create, whose "instances/copies" will be installed on multiple PCs of the client and are able to access the same database from another PC of the same client that has SQL server running all the time through the same network(i.e: they have the same router and static IP of server etc).
I had two ways to do this:
To make applications use the same database through synchronization.
To have multiple localdbs that then share the changes a database server.
By following 1st way,
I tried setting up the Connection String like:
SqlConnection con = new SqlConnection("Data Source =[serverPcIP,Port];Integrated Security=True;Connect Timeout=30");
SqlConnection con = new SqlConnection("SERVER=[serverPcIP]; Port=[portno];Integrated Security=True;Connect Timeout=30");
In Server - Security Settings:
I have allowed "SQL Server and Windows Authentication mode"
In Sql Server Configuration Manager > SQL Server Network Configuration > Protocols for SQLEXPRESS => TCP/IP = Enabled; under IP Addresses -> IP1 -> TCP Port = 1433 (port that i used in my connection-string)
In advanced Firewall Setting:
Have enabled the Incoming & Outgoing rules for port 1433.
The exception that i get:
Additional information: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: TCP Provider, error: 0 - The wait operation timed out.)
Can someone please tell me what configurations (either in connection-String or in SQL server itself) am i missing?

Your connection string lacks the instance name e.g. data source=<hostname or ip>\SQLEXPRESS. If your database listens on the default port 1433 you don't need to pass that with the connection string
If you setup a SQL server, you can choose between the default SQL Server instance or the named instance. For SQL Express the default is to install a named instance with the name SQLEXPRESS. If you don't use the default instance and install a named instance instead, you have to pass it with the connection string.
The default SQL Server instance ist just a named instance with the well known name MSSQLSERVER. So if you installed the database instance as the default instance you can connect with <host>[,port] or <host>\MSSQLSERVER[,port]

based on your screenshot, under IP1, the ip address is active but not enabled.
also, ip address that starts with 169.x.x.x normally would mean you have set up this network card to use DHCP, but the network card failed to have ip address from the DHCP server.
do you mind try to use static ip address?

Consider following steps:
Since you mention the port number using configuration manager, the service required restart. please restart the service if not done so.
Seems you are able to connect via SSMS, once service restarted verify SQL Error log via SSMS -> Managemnt -> SQL Server Logs, you must find a message as follows:
Server is listening on [ 'any' <ipv4> 1433].
Further details, follow these steps. Also, this..

How do I let multiple computers share a single database on a server?

I wrote a program to track the records of an employee in Windows Forms application in Visual Studio. I am using SQL Server 2017 Express for the data storage. My SqlConnection statement is using localhost and SQL Server authentication, what I need to know if how do I let multiple computers be in sync to a single database, there is no internet but the computers share a server where they can store files inside and all the computers can access it, I read somewhere that people input the ip address of the main computer in the SqlConnection statement but I'm not sure how that would work.
This is my SqlConnection statement currently
new sqlConnection(#"Data source = localhost\sqlexpress; Initial catalog = database;user id =sa;password = 1234; integrated security = false")
The program will be installed on multiple computers for people to use

First of all you have to change localhost with the host name or with the ip of the sql server hosting pc.
it will be something
new sqlConnection(#"Data source = mySqlServerPcName\sqlexpress; Initial catalog = database;user id =sa;password = 1234; integrated security = false")
then you have to enable tcp/ip on the sql server Configuration Manager on the hosting pc.
open sql server Configuration Manager
then go to SQL Server Network Configuration and click on Protocols for SQLEXPRESS.
Then you will see that TCP/IP is disabled. Double Click on TCP/IP and select yes to enabled. click ok and you will get the following message
press ok and click on the left side SQL Server Services. Right click the SQL Server(SQLEXPRESS) and select restart.
Now your SQL Server is ready.
Now the last thing you have to do is open the sql port on the firewall.
open a command line and run the following command
netsh advfirewall firewall add rule name = SQLPort dir = in protocol = tcp action = allow localport = 1433 remoteip = localsubnet profile = DOMAIN
Now you are ready to connect to the database from other computers.

Make sure that the sql server on a machine is accessible from all computers you intent the app to work. You also may have to open ports used by sql server in firewall. You can then update the connection string to connect to the sql instance.
Note: It can be a good idea to store connection string in a configuration file rather than in the code.

SQL Server problems to connect

I am developing a program with C# and WPF. I want the data to be stored in an SQL Server database. I made a connection string with the instance name in my PC, and that worked. But when I want to connect through the Internet with an IP address, I get some errors:
A network-related or instance-specific error occurred while
establishing a connection to SQL Server. The server was not found or
was not accessible Verify that the instance name is correct and that
SQL Server is configured to allow remote connections. (TCP Provider,
error 0 - No connection could be made because the target machine
actively refused it.)
I enabled TCP/IP, allowed remote connection in SQL Configuration Manager, opened a port of 1433 in my firewall, but still I am getting this error.
My connection string is this:
String connString = #"Network Library=dbmssocn;
Network Address=127.0.0.1,1433;
Integrated security=SSPI;
Initial Catalog=db";
SqlConnection conn = new SqlConnection(connString);
conn.Open( );
Where is my mistake?

There is very slight error in your connection string and honestly I can't blame you for that as it is very weird way in which SQL Sever is behaving. I'm not sure if this error lies in connection provider side or SQL Server instance side. Name of Network Library that your application is using to connect to the SQL Server using dbmssocn(Win32 Winsock TCP/IP) should always be mentioned in capital letters. Though I didn't see any relevant MSDN documentation from MS to support my statement but it actually worked when I did so. Here is the connection string that you should be using to fix the error.
String connString = #"Network Library=DBMSSOCN;
Network Address=127.0.0.1,1433;
Integrated security=SSPI;
Initial Catalog=db";
Seriously, I got freaked out in reproducing your issue as instead of copying the connection string from your question I copied it from some other blog :). But all is well that ends well. I've also assumed that a database named "db" actually exists on the default (NOT named instance) instance of the sql server you are connecting to when typing this answer. If changing the casing of network library name in connection string doesn't help then double check that database "db" must exist for a sql server default instance to which you are connecting to. In case you are using a named instance of sql server in your installation then that instance name should also come in the connection string.

Configure your SQL Server to allow TCP/IP connections. Go to SQL Server Configuration Manager -> network then protocols for your SQL Server named instance -> TCP/IP.
See this image!

The same connection succeed and fails in different .net solutions

I have two .net solutions.
They both have this code:
var connectionString = "Server = ServerName; Database = DatabaseName; Trusted_Connection=True;"
var connection = new SqlConnection(connectionString);
connection.Open();
connection.Close();
And they both use complitely the same connectionString. And they connect to MSSQL Server;
And in the first solution connection.Open() succeeded and in the second one it failed.
Error message : Named Pipes Provider, error: 40 - Could not open a connection to SQL Server
And every time I create new solution it fails. So this connection only works in one specific solution. And also, my teammates tested this and didn't have such issues.
Can you help with hints why it can be so?

Check that your SQL server has the TCP/IP protocol enabled and if it is using dynamic ports, ensure that the SQL Browser service is running.
Make sure that any firewall software (windows firewall etc.) has an exception added for the particular exe (the sqlservr.exe file gets copied into the instance folder, which will be in C:\Program Files\Microsoft SQL Server\{instance name}\MSSQL\Binn, where instance name might look something like MSSQL11.SQLEXPRESS) or TCP port 1433 or UDP port 1434 (TCP 1433 for the SQL service itself assuming standard settings, UPD 1434 for the SQL Browser Service).
Check that the user account used to access the server (it should also have sufficient permissions and the login should be enabled), in this case it will be whatever windows account you are logged in as or whatever account your IIS application pool is running as because you are using Trusted_Connection=True.
Also check that you have an up-to-date SQL Client on your machine, you can get the latest version for windows here.

Open Sql Server Configuration Manager and make sure that the Named Pipes option is enabled for your Sql server instance.

Sorry for disturbing you. My problem was my inattentiveness. I created soluiton on another network machine.

Can't connect to SQL Server 2005 Express from an ASP.NET C# page

I have an MS SQL Server 2005 Express running on a VPS.
I'm using pymssql in Python to connect to my server with the following code:
conn = pymssql.connect(host='host:port', user='me', password='pwd', database='db')
and it works perfectly.
When I try to connect to the server from an ASP.NET C# page with the following code:
SqlConnection myConnection = new SqlConnection("Data Source=host,port;Network Library=DBMSSOCN; Initial Catalog=db;User ID=me;Password=pwd;");
myConnection.Open();
When I run the ASP.NET page I get the following exception at myConnection.Open();:
A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: TCP Provider, error: 0 - A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.)
I tried restarting the SQL Server but I had no luck.
Can anyone point me out to what I'm missing here?
Thanks!

Let's say your host is localhost. When you are using SQLEXPRESS you need to specify that in your Instance Name.
Loke this: Data Source=localhost\SQLEXPRESS if it is bound to localhost. Otherwise it might just work with: Data Source=.\SQLEXPRESS.
If you have management studio installed you can fire that up and check what connection string it is using!

Still doesn't work..
I'm able to connect to the remote server with SQL Management Studio.
I enter host,port\SQLEXPRESS (of course I my actual IP number as the host and my actual port) in the Server Name field, select SQL Security and enter my username and password and it works perfectly.
When I try to connect from the ASP.NET page, it just doesn't work - I get the error aforementioned. Can it have something to do with the company hosting my asp.net page? (GoDaddy)
here is the code again..(assuming my host is 11.22.33.44 and my db is named bla
string connectString = #"Data Source=11.22.33.44,1433\SQLEXPRESS;Network Library=DBMSSOCN;Initial Catalog=bla;User ID=username;Password=pwd;";
SqlConnection myConnection = new SqlConnection(connectString);
myConnection.Open();
Thanks again