连接数据库异常:Connection refused

我用PL/SQL可以连接数据库，但是用杰表工具4.0连接，就报错，信息如下
java.sql.SQLException: Io 异常: Connection refused(DESCRIPTION=(ERR=1153)(VSNNUM=169870336)(ERROR_STACK=(ERROR=(CODE=1153)(EMFI=4)(ARGS='(ADDRESS=(PROTOCOL=TCP)(HOST=SSAIU488)(PORT=1521))'))(ERROR=(CODE=305)(EMFI=1))))
         at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:180)
         at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:222)
         at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:335)
         at oracle.jdbc.driver.OracleConnection.<init>(OracleConnection.java:361)
         at oracle.jdbc.driver.OracleDriver.getConnectionInstance(OracleDriver.java:442)
         at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:321)
         at java.sql.DriverManager.getConnection(DriverManager.java:582)
         at java.sql.DriverManager.getConnection(DriverManager.java:185)
         at com.jatools.data.rs.sql.ZConnection.getConnection(Unknown Source)
         at com.jatools.data.rs.sql.ZSqlReader.getConnection2(Unknown Source)
         at com.jatools.data.rs.sql.ZSqlReader.readStart(Unknown Source)
         at com.jatools.data.rs.ZRowSet.a(Unknown Source)
         at com.jatools.data.rs.ZRowSet.read(Unknown Source)
         at com.jatools.data.rs.ZRowSet.getInstance(Unknown Source)
         at com.jatools.designer.dh.b(Unknown Source)
         at com.jatools.designer.bv.a(Unknown Source)
         at com.jatools.designer.b.b.c.a(Unknown Source)
         at com.jatools.designer.b.b.d.setSelectedIndex(Unknown Source)