I have downloaded and installed DB2 Community server on Windows 11 desktop machine. But I am not able to connect to it using IBM DMC or a third-party software like DBeaver. I receive this error: A DRDA Data Stream Syntax Error was detected. Reason: 0x3. ERRORCODE=-4499, SQLSTATE=58009.
I have spent hours looking for solutions online, but none of those solutions worked (making sure JDBC driver is same as the DB2 version, disabling firewall etc.). 
Can anyone please help me solving this problem?
I should add that I am only able to connect to work with databases using db2cmd. Here is some information about my setup:
db2set -all
[e] DB2PATH=C:\DB2\IBM\SQLLIB
[i] DB2INSTPROF=C:\ProgramData\IBM\DB2\DB2COPY1
[i] DB2COMM=TCPIP
[g] DB2_EXTSECURITY=NO
[g] DB2_COMMON_APP_DATA_PATH=C:\ProgramData
[g] DB2SYSTEM=C102-LT-0308
[g] DB2PATH=C:\DB2\IBM\SQLLIB
[g] DB2INSTDEF=DB2
[g] DB2ADMINSERVER=DB2DAS00

What is your connection string?

What port Db2 is listening on?

What is DB2COMM environment variable set to?

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Jan Nelken
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jdbc:db2://{host}[:{port}]/{database} 

port 11080 (which is http port for DMC).

DBCOMM=TCPIP

Meanwhile, my DB2 version is 11.5.8000.317 and 11.5.8.0 is JDBC driver on DBeaver.

Thank you. Now it is resolved.

You asked me the right question which just led me to answer. my port number is actually 25000 and now its finally connected.