我正在学习套接字编程，我希望客户端何时连接到我的服务器。我可以通过他们的具体地址向他们发送数据..
例如
服务器--->客户端1
╚--->客户端2
╚--->客户端3
连接来源:192.168.5.3
连接来源:192.168.5.10
连接来自:192.168.5.15
例如，客户端 1 向我发送数据，然后客户端 2 也向我发送数据，我只想回复客户端 1，我怎么可能这样做？..
我将如何存储我的客户端，以便当我需要向他们发送数据时我知道我将向哪个客户端发送数据？
这是我的代码。
#include <stdio.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <errno.h>
#include <string.h>
#include <sys/select.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <poll.h>
#define TRUE 1
#define FALSE 0
typedef struct SERVER_FD{
int sPort;
int serverFD;
int smaxFD;
int newFD;
}sSD;
pid_t pid, sid;
int cFD,
dSize,
err,
start = 1,
state,
DescRead,
DCSERVER = FALSE;
int fd;
char buf[255];
int nbytes;
struct sockaddr_in addr, cli_addr;
unsigned long ip;
char strbuf[256];
socklen_t clilen;
fd_set fdin, fduse;
struct pollfd pfds[2];
int rc;
void process(int ServerFD, int Port, int sMax, int NewSFD);
void cleanUP(int i, int max);
void dlogs(unsigned long ip);
main (int argc, char *argv[])
{
sSD link;
sSD *sCon;
sCon = &link;
sCon->sPort = 53234;
fd = open("/tmp/myFIFO", O_RDWR);
if(fd == -1) {
printf("Could not open the pipe\n");
}
fcntl(fd, F_SETFL,
fcntl(fd, F_GETFL) |
O_NONBLOCK);
sCon->serverFD = socket(AF_INET, SOCK_STREAM, 0);
if (sCon->serverFD != -1)
{
err = setsockopt(sCon->serverFD, SOL_SOCKET, SO_REUSEADDR,(char *)&start, sizeof(start));
if (err != -1)
{
err = ioctl(sCon->serverFD, FIONBIO, (char *)&start);
if (err != -1){
process(sCon->serverFD,sCon->sPort,sCon->smaxFD,sCon->newFD);
}
else{
perror("ioctl() failed");
close(sCon->serverFD);
exit(EXIT_FAILURE);
}
}
else{
perror("setsockopt() failed");
close(sCon->serverFD);
exit(EXIT_FAILURE);
}
}
else{
perror("FAILED CONNECTING TO SOCKET");
exit(EXIT_FAILURE);
}
}
void process(int ServerFD, int Port, int sMax, int NewSFD){
bzero((char *) &addr, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = 0;
addr.sin_port = htons(Port);
err = bind(ServerFD,(struct sockaddr *)&addr, sizeof(addr));
if (err < 0)
{
perror("bind() failed");
close(ServerFD);
exit(EXIT_FAILURE);
}
err = listen(ServerFD, 32);
if (err < 0)
{
perror("listen() failed");
close(ServerFD);
exit(EXIT_FAILURE);
}
clilen = sizeof(cli_addr);
FD_ZERO(&fdin);
sMax = ServerFD;
FD_SET(ServerFD, &fdin);
do
{
fduse = fdin;
//printf("Waiting on select()...\n");
err = select(sMax + 1, &fduse, NULL, NULL, NULL);
if (err < 0)
{
perror(" select() failed");
break;
}
DescRead = err;
for (cFD=0; cFD <= sMax && DescRead > 0; ++cFD)
{
if (FD_ISSET(cFD, &fduse))
{
DescRead -= 1;
if (cFD == ServerFD)
{
//printf(" Listening socket is readable\n");
do
{
NewSFD = accept(ServerFD,(struct sockaddr *) &cli_addr, &clilen);
if (NewSFD < 0)
{
if (errno != EWOULDBLOCK)
{
perror(" accept() failed");
DCSERVER = TRUE;
}
break;
}
ip = ntohl(cli_addr.sin_addr.s_addr);
printf(" Connection from %d.%d.%d.%d\n",
(int)(ip>>24)&0xff,
(int)(ip>>16)&0xff,
(int)(ip>>8)&0xff,
(int)(ip>>0)&0xff);
dlogs(ip);
FD_SET(NewSFD, &fdin);
if (NewSFD > sMax)
sMax = NewSFD;
} while (NewSFD != -1);
}
else
{
//printf(" Descriptor %d is readable\n", cFD);
pfds[0].fd = fd;
pfds[0].events = POLLIN;
pfds[1].fd = cFD;
pfds[1].events = POLLIN;
state = FALSE;
do
{
rc = poll(pfds, 2, -1);
if (pfds[0].revents & POLLIN)
{
while ((nbytes = read(fd, buf, sizeof(buf)-1)) > 0)
{
buf[nbytes] = '\0';
printf("%s\n", buf);
}
pfds[0].events = 0;
pfds[1].events = POLLIN | POLLOUT;
}
if (pfds[1].revents & POLLIN)
{
err = recv(cFD, strbuf, sizeof(strbuf), 0);
if (err < 0)
{
if (errno != EWOULDBLOCK)
{
perror(" recv() failed");
state = TRUE;
}
break;
}
if (err == 0)
{
printf(" Connection closed\n");
state = TRUE;
break;
}
dSize = err;
printf(" %d bytes received\n", dSize);
}
if (pfds[1].revents & POLLOUT)
{
err = send(cFD, buf, strlen(buf), 0);
if (err < 0)
{
perror(" send() failed");
state = TRUE;
break;
}
pfds[0].events = POLLIN;
pfds[1].events = POLLIN;
}
} while (TRUE);
fopen("/sockF.txt","w");
if (state)
{
close(cFD);
FD_CLR(cFD, &fdin);
if (cFD == sMax)
{
while (FD_ISSET(sMax, &fdin) == FALSE)
sMax -= 1;
}
}
}
}
}
} while (DCSERVER == FALSE);
cleanUP(cFD, sMax);
}
void cleanUP(int i, int max){
for (i=0; i <= max; ++i)
{
if (FD_ISSET(i, &fdin))
close(i);
}
}
void dlogs(unsigned long ip){
FILE* pFile = fopen("/sockF.txt", "w+");
fprintf(pFile,"Connection from: %d.%d.%d.%d",
(int)(ip>>24)&0xff,
(int)(ip>>16)&0xff,
(int)(ip>>8)&0xff,
(int)(ip>>0)&0xff);
fclose(pFile);
}
客户端可以连接到我，但我不知道当两个客户端都连接时要发送数据...当只有 1 个客户端连接到我的服务器时我可以发送数据，但我如何将数据发送到另一个客户端当我的 2 个客户端同时连接时？
谢谢
最佳答案
首先 - 我想说它写得不好。但既然您正在学习，您就需要了解哪段代码在做什么。
NewSFD = accept(ServerFD,(struct sockaddr *) &cli_addr, &clilen);
NewSFD 是生成的新连接描述符/套接字，仅连接到向您发送消息的客户端。如果您在此描述符/套接字上进行写入/发送，它将被发送客户端接收。
char * response = "Connection echoed";
send(NewSFD, response, strlen(response), 0); // call returns number of bytes written.
如果您想在稍后的某个时刻执行此操作，则需要将此套接字保存在某个结构中并访问它以写入特定的客户端。
cli_addr 实际上会返回客户端信息，例如端口和 IP，后者可用于创建新的套接字。但是，您使用的 TCP 需要通过连接和接受调用进行握手。因此使用保存的连接套接字是合适的选择。
您可以使用这样的结构
typedef struct _client_fds{
int connected_sock; // copy the returned value of accept sock_addr_in cli_addr;
struct sock_add_in cli_addr // copy the client struct here
} client_fds;
client_fds 客户端[MAX]；
后者检索套接字以从中写入
关于c - 将数据发送到我的服务器中选定的客户端，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/13023829/