[resolved] exception java.net.ConnectException : Error opening socket to server Connection timed out.

The following error appears when using DB2 Data Studio to link to the server’s database: SQL4499N

Ensure that the data server has been started.
Check that the database name used is the actual database name and not an alias name.
Check that the host is a valid name or IP address, and that the port number is valid for communication with the data server.
To further diagnose the problem, return to the Properties section and use the Tracing page to enable tracing. Contact the 
database administrator and provide the trace and other support information available.
Full message content: [jcc][t4][2043][11550][4.13.111] Exception java.net.ConnectException: Error opening socket to server 
/127.0.0.1 on port 50,000 with message: Connection timed out.

When I went to the test server to check the connection, I found that I could not connect to the company’s internal network, so I could connect to the external network. Because I configured the static IP address.
Found that /etc/resolv.conf did not have a company gateway address. So after adding, you can connect the company Intranet. But the db2 connection problem remains.

Then checked the online information: https://www.ibm.com/developerworks/community/forums/html/topic?id=77777777-0000-0000-0000-000014881167#77777777-0000-0000-0000-000014882240

Enter the following command:
Db2set DB2COMM=tcpip, which is the command to set the db2 connection to tcpip
Db2 UPDATE DBM CFG using SVCENAME db2c_db2inst1, this command should be used to add the service name to db2’s config file. And then restart DB2

[[email protected] ~]$ db2set DB2COMM=tcpip
[[email protected] ~]$ db2stop
SQL1064N  DB2STOP processing was successful.
[[email protected] ~]$ db2start
SQL1063N  DB2START processing was successful.
[[email protected] ~]$ vi /etc/services

[[email protected] ~]$ db2 update dbm cfg using SVCENAME db2c_db2inst1
DB20000I  The UPDATE DATABASE MANAGER CONFIGURATION command completed 
successfully.
[[email protected] ~]$ db2stop
dbSQL1064N  DB2STOP processing was successful.
[[email protected] ~]$ db2start
SQL1063N  DB2START processing was successful.

Enter db2 get DBM CFG to see all of db2’s config

[[email protected] ~]$ db2 get dbm cfg

          Database Manager Configuration

     Node type = Database Server with local and remote clients

 Database manager configuration release level            = 0x0f00

 CPU speed (millisec/instruction)             (CPUSPEED) = 1.259585e-07

 Max number of concurrently active databases     (NUMDB) = 32
 Federated Database System Support           (FEDERATED) = NO
 Transaction processor monitor name        (TP_MON_NAME) = 

 Default charge-back account           (DFT_ACCOUNT_STR) = 

 Java Development Kit installation path       (JDK_PATH) = /home/db2inst1/sqllib/java/jdk64

 Diagnostic error capture level              (DIAGLEVEL) = 3
 Notify Level                              (NOTIFYLEVEL) = 3
 Diagnostic data directory path               (DIAGPATH) = /home/db2inst1/sqllib/db2dump/
 Current member resolved DIAGPATH                        = /home/db2inst1/sqllib/db2dump/
 Alternate diagnostic data directory path (ALT_DIAGPATH) = 
 Current member resolved ALT_DIAGPATH                    = 
 Size of rotating db2diag & notify logs (MB)  (DIAGSIZE) = 0

 Default database monitor switches
   Buffer pool                         (DFT_MON_BUFPOOL) = OFF
   Lock                                   (DFT_MON_LOCK) = OFF
   Sort                                   (DFT_MON_SORT) = OFF
   Statement                              (DFT_MON_STMT) = OFF
   Table                                 (DFT_MON_TABLE) = OFF
   Timestamp                         (DFT_MON_TIMESTAMP) = ON
   Unit of work                            (DFT_MON_UOW) = OFF
 Monitor health of instance and databases   (HEALTH_MON) = OFF

 SYSADM group name                        (SYSADM_GROUP) = DB2IADM1
 SYSCTRL group name                      (SYSCTRL_GROUP) = 
 SYSMAINT group name                    (SYSMAINT_GROUP) = 
 SYSMON group name                        (SYSMON_GROUP) = 

 Client Userid-Password Plugin          (CLNT_PW_PLUGIN) = 
 Client Kerberos Plugin                (CLNT_KRB_PLUGIN) = 
 Group Plugin                             (GROUP_PLUGIN) = 
 GSS Plugin for Local Authorization    (LOCAL_GSSPLUGIN) = 
 Server Plugin Mode                    (SRV_PLUGIN_MODE) = UNFENCED
 Server List of GSS Plugins      (SRVCON_GSSPLUGIN_LIST) = 
 Server Userid-Password Plugin        (SRVCON_PW_PLUGIN) = 
 Server Connection Authentication          (SRVCON_AUTH) = NOT_SPECIFIED
 Cluster manager                                         = 

 Database manager authentication        (AUTHENTICATION) = SERVER
 Alternate authentication           (ALTERNATE_AUTH_ENC) = NOT_SPECIFIED
 Cataloging allowed without authority   (CATALOG_NOAUTH) = NO
 Trust all clients                      (TRUST_ALLCLNTS) = YES
 Trusted client authentication          (TRUST_CLNTAUTH) = CLIENT
 Bypass federated authentication            (FED_NOAUTH) = NO

 Default database path                       (DFTDBPATH) = /home/db2inst1

 Database monitor heap size (4KB)          (MON_HEAP_SZ) = AUTOMATIC(90)
 Java Virtual Machine heap size (4KB)     (JAVA_HEAP_SZ) = 2048
 Audit buffer size (4KB)                  (AUDIT_BUF_SZ) = 0
 Size of instance shared memory (4KB)  (INSTANCE_MEMORY) = AUTOMATIC(1048576)
 Instance memory for restart light (%) (RSTRT_LIGHT_MEM) = AUTOMATIC(10)
 Agent stack size                       (AGENT_STACK_SZ) = 1024
 Sort heap threshold (4KB)                  (SHEAPTHRES) = 0

 Directory cache support                     (DIR_CACHE) = YES

 Application support layer heap size (4KB)   (ASLHEAPSZ) = 15
 Max requester I/O block size (bytes)         (RQRIOBLK) = 32767
 Workload impact by throttled utilities(UTIL_IMPACT_LIM) = 10

 Priority of agents                           (AGENTPRI) = SYSTEM
 Agent pool size                        (NUM_POOLAGENTS) = AUTOMATIC(100)
 Initial number of agents in pool       (NUM_INITAGENTS) = 0
 Max number of coordinating agents     (MAX_COORDAGENTS) = AUTOMATIC(200)
 Max number of client connections      (MAX_CONNECTIONS) = AUTOMATIC(MAX_COORDAGENTS)

 Keep fenced process                        (KEEPFENCED) = YES
 Number of pooled fenced processes         (FENCED_POOL) = AUTOMATIC(MAX_COORDAGENTS)
 Initial number of fenced processes     (NUM_INITFENCED) = 0

 Index re-creation time and redo index build  (INDEXREC) = RESTART

 Transaction manager database name         (TM_DATABASE) = 1ST_CONN
 Transaction resync interval (sec)     (RESYNC_INTERVAL) = 180

 SPM name                                     (SPM_NAME) = oc335442
 SPM log size                          (SPM_LOG_FILE_SZ) = 256
 SPM resync agent limit                 (SPM_MAX_RESYNC) = 20
 SPM log path                             (SPM_LOG_PATH) = 

 TCP/IP Service name                          (SVCENAME) = db2c_db2inst1
 Discovery mode                               (DISCOVER) = SEARCH
 Discover server instance                (DISCOVER_INST) = ENABLE

 SSL server keydb file                   (SSL_SVR_KEYDB) = 
 SSL server stash file                   (SSL_SVR_STASH) = 
 SSL server certificate label            (SSL_SVR_LABEL) = 
 SSL service name                         (SSL_SVCENAME) = 
 SSL cipher specs                      (SSL_CIPHERSPECS) = 
 SSL versions                             (SSL_VERSIONS) = 
 SSL client keydb file                  (SSL_CLNT_KEYDB) = 
 SSL client stash file                  (SSL_CLNT_STASH) = 

 Maximum query degree of parallelism   (MAX_QUERYDEGREE) = ANY
 Enable intra-partition parallelism     (INTRA_PARALLEL) = NO

 No. of int. communication buffers(4KB)(FCM_NUM_BUFFERS) = AUTOMATIC(1024)
 No. of int. communication channels   (FCM_NUM_CHANNELS) = AUTOMATIC(512)
 db2start/db2stop timeout (min)        (START_STOP_TIME) = 10

 WLM dispatcher enabled                 (WLM_DISPATCHER) = NO
 WLM dispatcher concurrency            (WLM_DISP_CONCUR) = COMPUTED
 WLM dispatcher CPU shares enabled (WLM_DISP_CPU_SHARES) = NO
 WLM dispatcher min. utilization (%) (WLM_DISP_MIN_UTIL) = 5

 Communication buffer exit library list (COMM_EXIT_LIST) = 

If you only see if the service was added successfully:

[[email protected] ~]$ db2 get dbm cfg|grep SVC
 TCP/IP Service name                          (SVCENAME) = db2c_db2inst1
 SSL service name                         (SSL_SVCENAME) = 

Restart DB and the problem remains.

Later, I saw other materials on the Internet and said that it would not be the problem of the firewall… Then I looked at the firewall…

Computer-> Control Center-> Firewall-> Other Ports
Click the + sign, then in the popup dialog find Port 50000 | Protocal TCP | Service db2c_db2inst1, click OK. Click on the green in the upper left corner and check Apply.

Go back to Data Studio and try to connect again. The connection is successful!
Sure enough, it’s the firewall again… Lift the table!

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