《TCP/IP网络编程》第9章

• 套接字可选项
• SO_REUSEADDR
• TCP_NODELAY
• Windows实现

套接字可选项

#include <sys/socket.h>
//成功0，失败-1
int getsockopt(int sock, int level, int optname, void *optval, socklen_t *optlen);
//成功0，失败-1
int setsockopt(int sock, int level, int optname, const void *optval, socklen_t *optlen);

sock_type.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/socket.h>

void error_handling(char *message);

int main(int argc, char *argv[]) {
	int tcp_sock;
	int udp_sock;
	int sock_type;
	socklen_t optlen;
	int state;

	optlen = sizeof(sock_type);
	tcp_sock = socket(PF_INET, SOCK_STREAM, 0);
	udp_sock = socket(PF_INET, SOCK_DGRAM, 0);
	printf("SOCK_STREAM: %d\n", SOCK_STREAM);
	printf("SOCK_DGRAM: %d\n", SOCK_DGRAM);

	state = getsockopt(tcp_sock, SOL_SOCKET, SO_TYPE, (void*)sock_type, &optLen);
	if(state)
		error_handling("getsockopt() error");
	printf("Socket type one: %d\n", sock_type);
	
	state = getsockopt(udp_sock, SOL_SOCKET, SO_TYPE, (void*)sock_type, &optLen);
	if(state)
		error_handling("getsockopt() error");
	printf("Socket type two: %d\n", sock_type);
	return 0;
}


void error_handling(char *message) {
	fputs(message, stderr);
	fputc('\n', stderr);
	exit(1);
}

gcc sock_type.c -o socktype
./socktype

get_buf.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/socket.h>

void error_handling(char *message);

int main(int argc, char *argv[]) {
	int sock;
	int snd_buf;
	int rcv_buf;
	int state;
	socklen_t len;

	sock = socket(PF_INET, SOCK_STREAM, 0);
	len = sizeof(snd_buf);

	//输出缓冲大小
	state = getsockopt(sock, SOL_SOCKET, SO_SNDBUF, (void*)snd_buf, &len);
	if(state)
		error_handling("getsockopt() error");
	printf("Input buffer size: %d\n", rcv_buf);	
		
	//输入缓冲大小
	state = getsockopt(sock, SOL_SOCKET, SO_RCVBUF, (void*)rcv_buf, &len);
	if(state)
		error_handling("getsockopt() error");
	printf("Output buffer size: %d\n", snd_buf);	
	
	return 0;
}


void error_handling(char *message) {
	fputs(message, stderr);
	fputc('\n', stderr);
	exit(1);
}

gcc get_buf.c -o getbuf
./getbuf

set_buf.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/socket.h>

void error_handling(char *message);

int main(int argc, char *argv[]) {
	int sock;
	int snd_buf=1024*3;
	int rcv_buf=104*3;
	int state;
	socklen_t len;

	sock = socket(PF_INET, SOCK_STREAM, 0);
	state = setsockopt(sock, SOL_SOCKET, SO_SNDBUF, (void*)snd_buf, sizeof(snd_buf));
	if(state)
		error_handling("setsockopt() error");
	state = setsockopt(sock, SOL_SOCKET, SO_RCVBUF, (void*)rcv_buf, sizeof(rcv_buf));
	if(state)
		error_handling("setsockopt() error");

	len = sizeof(snd_buf);

	//输出缓冲大小
	state = getsockopt(sock, SOL_SOCKET, SO_SNDBUF, (void*)snd_buf, &len);
	if(state)
		error_handling("getsockopt() error");
	printf("Input buffer size: %d\n", rcv_buf);	
		
	//输入缓冲大小
	state = getsockopt(sock, SOL_SOCKET, SO_RCVBUF, (void*)rcv_buf, &len);
	if(state)
		error_handling("getsockopt() error");
	printf("Output buffer size: %d\n", snd_buf);	
	
	return 0;
}

void error_handling(char *message) {
	fputs(message, stderr);
	fputc('\n', stderr);
	exit(1);
}

gcc set_buf.c -o setbuf
./setbuf

SO_REUSEADDR

先断开连接（先发送FIN消息）的主机经历Time-wait状态（套接字延迟释放，确保对方收到最后的ACK消息），此时相应端口是正在使用状态。

reuseaddr_eserver.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>

#define TRUE 1
#define FALSE 0
void error_handling(char *message);

int main(int argc, char *argv[]) {
	int serv_sock;
	int clnt_sock;
	char message[30];
	int option;
	int opt_len;
	int str_len;

	struct sockaddr_in serv_addr;
	struct sockaddr_in clnt_addr;
	socklen_t addr_size;

	if(argc!=2) {
		printf("Usage : %s <port>\n", argv[0]);
		exit(1);
	}

	serv_sock = socket(PF_INET, SOCK_STREAM, 0);
	if(serv_sock==-1)
		error_handling("socket() error");
		
	opt_len = sizeof(option);
	optiont = TRUE;
	setsockopt(serv_sock, SOL_SOCKET, SO_REUSEADDR, (void *)&option, opt_len);

	addr_size = sizeof(struct sockaddr_in);
	
	memset(&serv_addr, 0, addr_size);
	serv_addr.sin_family = AF_INET;
	serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
	serv_addr.sin_port = htons(atoi(argv[1]));
	
	if(bind(serv_sock, (struct sockaddr*)&serv_addr, addr_size)==-1)
		error_handling("bind() error");
		
	if(listen(serv_sock, 5)==-1)
		error_handling("listen() error");
		
	for(i=0; i<5; i++) {
		clnt_sock = accept(serv_sock, (struct sockaddr*)&clnt_addr, &addr_size );
		if(clnt_sock==-1)
			error_handling("accept() error");
		else
			printf("Connected client %d\n", i+1);
			
		while((str_len=read(clnt_sock, message, BUF_SIZE))!=0)
			write(clnt_sock, message, str_len);
			
		close(clnt_sock);
	}
	
	close(serv_sock);
	return 0;
}


void error_handling(char *message) {
	fputs(message, stderr);
	fputc('\n', stderr);
	exit(1);
}

gcc reuseaddr_eserver.c -o reserver
./reserver 9190
//Connected client 1
//Connected client 2
//Connected client 3

TCP_NODELAY

• TCP套接字默认使用Nagle算法交换数据，最大限度地进行缓冲，直到收到ACK，防止数据包过多发生网络过载（影响传输），提高网络传输效率。

• “大文件数据”应禁用Nagle算法，可以提高传输速度，类似于并行传输，不用等上一个数据包收到ACK后再发送下一个数据包，可以同时发送多个数据包。

int opt_val=1;
setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, (void *)&opt_val, sizeof(opt_val));

int opt_val;
socklen_t opt_len=sizeof(opt_val);
getsockopt(sock, IPPROTO_TCP, TCP_NODELAY, (void *)&opt_val, &opt_val);

Windows实现

#include <winsock2.h>
//成功0，失败SOCKET_ERROR
int getsockopt(SOCKET sock, int level, int optname, char *optval, int *optlen);
//成功0，失败-1
int setsockopt(SOCKET sock, int level, int optname, const char *optval, int optlen);

buf_win.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <winsock2.h>

void ErrorHanding(char *message);

int main(int argc, char *argv[]) {
	WSADATA wsaData;
	SPCKET sock;
	int snd_buf=1024*3;
	int rcv_buf=104*3;
	int state;

	if(WSAStartup(MAKEWORD(2, 2), &wsaData)!=0)
		ErrorHanding("WSAStartup() error!");
		
	sock = socket(PF_INET, SOCK_STREAM, 0);
	ShorSocketBufSize(sock);
	
	state = setsockopt(sock, SOL_SOCKET, SO_SNDBUF, (char*)&snd_buf, sizeof(snd_buf));
	if(state==SOCKET_ERROR)
		error_handling("setsockopt() error");
		
	state = setsockopt(sock, SOL_SOCKET, SO_RCVBUF, (char*)&rcv_buf, sizeof(rcv_buf));
	if(state==SOCKET_ERROR)
		error_handling("setsockopt() error");
		
	ShorSocketBufSize(sock);
	
	closesocket(sock);
	
	WSACleanup();
	return 0;
}

void ShorSocketBufSize(SOCKET sock) {
	int snd_buf;
	int rcv_buf;
	int state;
	int len;

	len=sizeof(snd_buf);
	state = getsockopt(sock, SOL_SOCKET, SO_SNDBUF, (char*)&snd_buf, &len);
	if(state==SOCKET_ERROR)
		error_handling("getsockopt() error");
	printf("Output buffer size: %d\n", snd_buf);	
		
	len=sizeof(rcv_buf);
	state = getsockopt(sock, SOL_SOCKET, SO_RCVBUF, (char*)&rcv_buf, &len);
	if(state==SOCKET_ERROR)
		error_handling("getsockopt() error");
	printf("Input buffer size: %d\n", rcv_buf);	
}

void ErrorHanding(char *message) {
	fputs(message, stderr);
	fputc('\n', stderr);
	exit(1);
}

gcc buf_win.c -o buf_win
./buf_win