如何关闭对write()系统调用的缓冲? [英] How to turn off buffering on write() system call?
问题描述
我常想,的write()
系统调用是缓冲和 FWRITE
和 FREAD
用于缓冲的IO。但是我写的简单程序,建立一些缓冲仍在继续使用写入时()
。我使用的write()
和阅读()
上的插座。由于缓冲,能够为客户端落后而服务器保持发送数据包。我不要那个。我想服务器发送更多的记录之前,客户必须消耗记录。
我怎样才能做到这一点无需添加确认等网络负荷!
我在Linux上使用的gcc
server.c:
的#include<&stdio.h中GT;
#包括LT&;&errno.h中GT;
#包括LT&; SYS / socket.h中>
#包括LT&; ARPA / inet.h>
#包括LT&;&stdio.h中GT;
#包括LT&; netinet / in.h中>
#包括LT&;&string.h中GT;
#包括LT&;&stdlib.h中GT;
#包括LT&;&stdio.h中GT;
#包括LT&;&unistd.h中GT;
#包括LT&; netinet / tcp.h中>INT remote_rr_port = 2000; //服务器将发送使用此端口上连接RR日志。
字符常量* remote_server_ip =127.0.0.1;
INT connFD_rr;
静态无效startTcpServer为(int * SD,const int的端口){
* SD =插座(AF_INET,SOCK_STREAM,0); //设置套接字选项,以便端口可以被重用
INT启用= 1;
setsockopt的(* SD,SOL_SOCKET,SO_REUSEADDR,&安培;启用的sizeof(INT));
结构有sockaddr_in一个;
memset的(&放大器;一,0,sizeof的(一));
a.sin_family = AF_INET;
a.sin_port =口;
a.sin_addr.s_addr = INADDR_ANY;
INT bindResult =绑定(* SD(结构sockaddr *)及一,的sizeof(一));
听(* SD,2);
}
//等待来自客户端的连接
静态INT getTcpConnection(INT SD){
焦炭BUF [100];
socklen_t的LEN;
结构SOCKADDR_IN clientAddress;
的printf(\\ nWaiting从远程客户端\\ n连接);
LEN = sizeof的(clientAddress);
INT connFD =接受(SD,(结构sockaddr *)及clientAddress,和放大器; LEN);
setsockopt的(connFD_rr,SOL_SOCKET,SO_SNDBUF(INT []){0},的sizeof(INT));
的printf(%S:从\\ n连接%d个\\ N,inet_ntop(AF_INET,&安培; clientAddress.sin_addr,BUF,sizeof的(BUF)),clientAddress.sin_port);
fflush(标准输出);
返回connFD;
}FILE * rdrr_server_start(无效){ //套接字描述符的两个连接
INT rr_sd;
INT input_sd; startTcpServer(安培; rr_sd,remote_rr_port); connFD_rr = getTcpConnection(rr_sd); 返回fdopen(connFD_rr,W);
}诠释主(){
INT I = 0;
rdrr_server_start(); 对于(i = 0; I<千万,我++){
写(connFD_rr,和放大器;我的sizeof(INT));
的printf(%d个\\ N,I);
}
返回0;
}
client.c:
的#include< SYS / socket.h中>
#包括LT&; ARPA / inet.h>
#包括LT&;&stdio.h中GT;
#包括LT&; netinet / in.h中>
#包括LT&;&string.h中GT;
#包括LT&;&stdlib.h中GT;
#包括LT&;&stdio.h中GT;
#包括LT&;&unistd.h中GT;
#包括LT&; netinet / tcp.h中>INT remote_rr_port = 2000; //服务器将发送使用此端口上连接RR日志。
字符常量* remote_server_ip =127.0.0.1;
INT connFD_rr;FILE * rdrr_client_start(无效){ connFD_rr =插座(AF_INET,SOCK_STREAM,0); 结构有sockaddr_in一个;
memset的(&放大器;一,0,sizeof的(一));
a.sin_family = AF_INET;
a.sin_port = remote_rr_port;
a.sin_addr.s_addr = inet_addr(remote_server_ip); 的printf(\\ nConnecting到RR端口上服务器);
INT CONNECT_TO_SERVER =连接(connFD_rr,(结构sockaddr *)及一,的sizeof(一));
的printf(\\ nConnected到RR端口上服务器);
setsockopt的(connFD_rr,SOL_SOCKET,SO_RCVBUF,(INT []){0},的sizeof(INT));
返回fdopen(connFD_rr,R);
}诠释主(){
INT I = 0;
rdrr_client_start();
getrchar();
而(1){
阅读(connFD_rr,和放大器;我的sizeof(INT));
的printf(%d个\\ N,I);
}
返回0;
}
也许你的意思是,你要禁用的 Nagle算法的在这种情况下,解决方案是:
的setsockopt(袜子,IPPROTO_TCP,TCP_NODELAY,(INT []){1},的sizeof(INT));
编辑:嗯,它看起来像你想比这更多,我怀疑你想要什么是可能的,而不在UDP上设计自己的协议
编辑2::您可以通过限制发送来获得类似于你想要的效果和接收缓冲区大小。服务器(发送方)应该做的:
的setsockopt(袜子,SOL_SOCKET,SO_SNDBUF(INT []){} YOUR_BUF_LIMIT,sizeof的(INT));
和客户端(接收器)应该做的:
的setsockopt(袜子,SOL_SOCKET,SO_RCVBUF,(INT []){} YOUR_BUF_LIMIT,sizeof的(INT));
I used to think that write()
system call is unbuffered and that fwrite
and fread
are used for buffered IO. However I wrote simple programs to establish that some buffering was still going on when using write()
. I am using write()
and read()
on sockets. Due to buffering, it is possible for the client to lag behind while server keeps sending packets. I do not want that. I want that the client must consume the record before the server sends more records.
How can I make that happen without adding network load of acknowledgments etc !
I am using gcc on linux
server.c :
#include <stdio.h>
#include <errno.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <netinet/in.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <netinet/tcp.h>
int remote_rr_port=2000; // Server will send RR logs using connection on this port.
char const *remote_server_ip="127.0.0.1";
int connFD_rr;
static void startTcpServer(int *sd, const int port) {
*sd= socket(AF_INET, SOCK_STREAM, 0);
// Set socket option so that port can be reused
int enable = 1;
setsockopt(*sd, SOL_SOCKET, SO_REUSEADDR, &enable, sizeof(int));
struct sockaddr_in a;
memset(&a,0,sizeof(a));
a.sin_family = AF_INET;
a.sin_port = port;
a.sin_addr.s_addr = INADDR_ANY;
int bindResult = bind(*sd, (struct sockaddr *) &a, sizeof(a));
listen(*sd,2);
}
// Wait for connection from client
static int getTcpConnection(int sd) {
char buf[100];
socklen_t len;
struct sockaddr_in clientAddress;
printf("\nWaiting for connection from remote client\n");
len = sizeof(clientAddress);
int connFD = accept(sd, (struct sockaddr*) &clientAddress, &len);
setsockopt(connFD_rr, SOL_SOCKET, SO_SNDBUF, (int[]){0}, sizeof(int));
printf("\n Connection from : %s:%d\n",inet_ntop(AF_INET, &clientAddress.sin_addr, buf, sizeof(buf)),clientAddress.sin_port);
fflush(stdout);
return connFD;
}
FILE* rdrr_server_start(void) {
// Socket Descriptors for the two connections
int rr_sd;
int input_sd;
startTcpServer(&rr_sd, remote_rr_port);
connFD_rr = getTcpConnection(rr_sd);
return fdopen(connFD_rr, "w");
}
int main() {
int i = 0;
rdrr_server_start();
for(i=0;i<10000000; i++) {
write(connFD_rr, &i, sizeof (int));
printf("%d\n", i);
}
return 0;
}
client.c :
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <netinet/in.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <netinet/tcp.h>
int remote_rr_port=2000; // Server will send RR logs using connection on this port.
char const *remote_server_ip="127.0.0.1";
int connFD_rr;
FILE* rdrr_client_start(void) {
connFD_rr = socket(AF_INET, SOCK_STREAM, 0);
struct sockaddr_in a;
memset(&a,0,sizeof(a));
a.sin_family = AF_INET;
a.sin_port = remote_rr_port;
a.sin_addr.s_addr = inet_addr(remote_server_ip);
printf("\nConnecting to Server on RR port");
int CONNECT_TO_SERVER= connect(connFD_rr,(struct sockaddr *) &a, sizeof(a));
printf("\nConnected to server on RR port");
setsockopt(connFD_rr, SOL_SOCKET, SO_RCVBUF, (int[]){0}, sizeof(int));
return fdopen(connFD_rr, "r");
}
int main() {
int i = 0;
rdrr_client_start();
getrchar();
while(1) {
read(connFD_rr, &i, sizeof (int));
printf("%d\n", i);
}
return 0;
}
Perhaps what you mean is that you want to disable Nagle's Algorithm in which case the solution is:
setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, (int[]){1}, sizeof(int));
Edit: Hmm, it looks like you want more than this, and I doubt what you want is possible without designing your own protocol on top of UDP.
Edit 2: You may be able to get an effect similar to what you want by limiting the send and receive buffer sizes. The server (sender) should do:
setsockopt(sock, SOL_SOCKET, SO_SNDBUF, (int[]){YOUR_BUF_LIMIT}, sizeof(int));
and the client (receiver) should do:
setsockopt(sock, SOL_SOCKET, SO_RCVBUF, (int[]){YOUR_BUF_LIMIT}, sizeof(int));
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