Unix Network Programming, Volume 1

搞出了个bug，回来重新翻书：4.4 bind Function A process can bind a specific IP address to its socket. The IP address must belong to an interface on the host. For a TCP client, this assigns the source IP address that will be used for IP datagrams sent on the socket. For a TCP server, this restricts the socket to receive incoming client connections destined only to that IP address.tcp服务端ip地址绑定说明：1. 服务器上可能有多个ip地址3. 给服务端socket绑定特定地址的话，客户端只能用这个地址来连接服务端4. 若无地址绑定，则用服务端的任意一个ip地址都可以被客户端连接（假设没防火墙拦截等其他特殊情况）If a TCP server does not bind an IP address to its socket, the kernel uses the destination IP address of the client's SYN as the server's source IP address (p. 943 of TCPv2).

++++++++++++++++ 问题 ++++++++++++++++++++++++++练习6.2 如果是阻塞的socket，是否可以先知道可写的buffer剩余大小BufLeft，然后发送<=BufLeft就避免阻塞了?6.8中.The server will call read, which will read the single byte of data from the client and then block in the next call to read, waiting for more data from this client. 为什么读了一个字节就被阻塞了? read()读到换行符才返回？ex8.1 为了一次读最多, datagram的最大长度可以设为多大?ex8.5 It probably has a socket receive buffer size, but data is never accepted for a listening TCP socket. 这么说来数据没被缓存到buffer中，那么如果同时很多请求过来，这些不被缓存的请求不是很容易丢失? 难道listening socket可以及时处理?丢包的最小单位是什么?After five seconds, SIGALRM is generated, our signal handler is called, and recvfrom returns the error EINTR. 信号导致recvfrom返回错误？++++++++++++++++++++++收获+++++++++++++++++++ex8.1 A recvfrom on a datagram socket never returns more than one datagram, regardless of how much the application asks for.2.6 tcp的发2个包:A,B. B是等A的ack到达发送端了才能发出去，还是AB可以一起发，然后一起等待ack？ 可以一起发the protocol can use variable-length socket address structures.tcp无法广播、多播SO_RCVBUF为什么只设置一次?(只能设一次: This is because of TCP's window scale option (Section 2.6), which is exchanged with the peer on the SYN segments when the connection is established. For a client, this means the SO_RCVBUF socket option must be set before calling connect.For a server, this means the socket option must be set for the listening socket before calling listen.) 为什么server不能在listen完后设置？因为listen后，一旦有client连接过来就会进行三次握手交换syn，交换syc后再设置SO_RCVBUF已经迟了This is a property of broadcasts: By definition, a broadcast goes to every host on the subnet, which includes the sender.In general, however, there is no requirement that a process bind a UDP port to which it sends datagrams.不绑定端口就不会收到了Also, broadcasting is normally limited to a LAN, whereas multicasting can be used on a LAN or across a WAN. use select you can design a sleep of millisecond(original sleep's unit is second)socket和端口是1对1的，不能1对多或多对1