【探索Linux】P.38（传输层 —— TCP协议通信连接管理机制简介 | TCP连接状态转换）

+----------+
                          |  CLOSED  |
                          +----------+
                             |     ^
                             v     |
                          +----------+
                          |  LISTEN  |
                          +----------+
                             |     ^
                             v     |
                          +----------+
                          |  SYN_RCVD|
                          +----------+
                             |     ^
                             v     |
        +------------------+-----------+
        |                  |           |
        v                  v           v
  +----------+          +----------+    +----------+
  |  SYN_SENT|          | SYN_SENT|    |  CLOSED  |
  +----------+          +----------+    +----------+
       |                    |               |     ^
       v                    v               v     |
+---------------+          +---------------+      |
|     ESTAB     |          |     ESTAB     |      |
|               |          |               |      |
|               |          |               |      |
+---------------+          +---------------+      |
       |                    |               |      |
       v                    v               v      |
+---------------+          +---------------+      |
|    FIN_WAIT1  |          |    FIN_WAIT2  |      |
+---------------+          +---------------+      |
       |                    |               |      |