Write Back

• to send data
• write method will be blocked buffer is too smaller to send data of len, until one of three situations has happened:
  • buffer is enough
  • connection is reset, return error
  • received a signal of interruption, return error (errno = EINTR)

1. write()

method

int write(int fd, char* buf, int len)

parameters

• fd: socket描述符
• buf: 發送緩衝區
• len: 要發送數據的長度

return value

• >=0: success

  • len: the length of buffer is greater than len

• -1: failure

• errno: wrong code

2. send()

method

int send(int sockfd, void buf, int len, int flags)

parameters

• fd: socket描述符
• buf: 接受緩衝區
• len: 接受數據長度
• flags: 接受數據的控制參數
  • 0: read()
  • MSG_DONTROUTE: 發送數據時不查找路由表, 適用於局域網
  • MSG_OOB: 發送帶外數據

return value

• >=0: success
• -1: failure
• errno: wrong code

3. writev()

• 寫多個非連續緩衝區, 稱為聚集寫

4. sendmsg()

• 類似於send, 但功能更強大