无法使sigaction工作

我正在尝试创建两个程序：一个基本的套接字服务器和一个客户端，这两个程序都将在Linux机器上运行。服务器的指令是设置一个套接字，接受传入的客户端请求，使用信号设置一个处理程序(用于读取数据缓冲区)，并进入无限睡眠循环。客户端的指令是设置一个套接字，连接到服务器，并发送一个数据缓冲区。在担心关闭连接和启动新连接之前，我想让它像针对单个客户端连接所描述的那样工作(还不确定这些东西应该循环到哪里，我正在努力保持简单。)我还了解到信号是不推荐使用的，所以我试着按照这里的示例使用sigaction：

http://www.linuxprogrammingblog.com/code-examples/sigaction

不幸的是，当我运行代码时会发生这样的情况：

1. 服务器启动
2. 服务器设置套接字
3. 服务器开始侦听并在接受时阻止(等待客户端)
4. 客户端启动
5. 客户端设置套接字
6. 客户端连接到服务器
7. 服务器取消阻止
8. 服务器设置sigaction
9. 服务器开始休眠
10. 客户端调用写入
11. 客户似乎写得很成功(上帝知道去哪里)
12. 客户端块正在等待来自服务器的字节读取确认
13. 服务器仍在休眠(sigaction从未触发)

这是我当前的服务器代码：

#include <sys/types.h>    // socket, bind
#include <sys/socket.h>   // socket, bind, listen, inet_ntoa
#include <netinet/in.h>   // htonl, htons, inet_ntoa
#include <arpa/inet.h>    // inet_ntoa
#include <netdb.h>        // gethostbyname
#include <unistd.h>       // read, write, close
#include <string.h>       // bzero
#include <netinet/tcp.h>  // SO_REUSEADDR
#include <sys/uio.h>      // writev
#include <signal.h>       // sigaction
#include <sys/time.h>     // gettimeofday
#include <unistd.h>       // write
#include <fcntl.h>        // fcntl
#include <iostream>       // cout
using namespace std;
#define BUFSIZE 1500
// Globals
int nreps;
int nbufs;
int newSd;
// Read all the data from the client and output how long it took
void readFromClient(int sig, siginfo_t *siginfo, void *context)
{
cout << "readFromClient triggered!" << endl;
/*
// Set up asynchronous communication
int fd = siginfo->si_fd;
fcntl(fd, F_SETOWN, getpid());
fcntl(fd, F_SETFL, FASYNC);
*/
// Declare data buffer
char databuf[BUFSIZE];
// Record start time
struct timeval theTime;
gettimeofday(&theTime, NULL);
int startTime = theTime.tv_usec + theTime.tv_sec * 1000000;
// Keep reading until the buffer is full
int nRead = 0;
/*
while((nRead += read(newSd, databuf, BUFSIZE - nRead)) < BUFSIZE)
{
cout << "nRead now: " << nRead << endl;
}
*/
// For testing single byte read
cout << "Reading a byte... " << endl;
char bytebuf[1];
read(newSd, bytebuf, 1);
cout << "SUCCESS" << endl;
// Record finish time
gettimeofday(&theTime, NULL);
int finishTime = theTime.tv_usec + theTime.tv_sec * 1000000;
// Calculate the receiving time
int receiveTime = finishTime - startTime;
// Display the receiving time
cout << "data-receiving time = " << receiveTime << " usec" << endl;
// Tell the client how much data was read
cout << "Writing amount read... " << endl;
write(newSd, (void*)nRead, 4);
cout << "SUCCESS" << endl;
// Close the socket
cout << "Closing socket... " << endl;
close(newSd);
cout << "SUCCESS" << endl;
// Exit the program
cout << "Exiting!" << endl;
exit(0);
cout << "Why are you still here?" << endl;
}
int main(int argc, char *argv[])
{
cout << "Server is running!" << endl;
// Store command line arguments
int port = atoi(argv[1]);
int nreps = atoi(argv[2]);
int nbufs = atoi(argv[3]);
cout << "port: " << port << endl;
cout << "nreps: " << nreps << endl;
cout << "nbufs: " << nbufs << endl;
// Declare a socket
sockaddr_in acceptSockAddr;
memset((char*)&acceptSockAddr, '', sizeof(acceptSockAddr));
acceptSockAddr.sin_family = AF_INET; // Address Family Internet
acceptSockAddr.sin_addr.s_addr = htonl(INADDR_ANY);
acceptSockAddr.sin_port = htons(port); // convert host byte-order
// Open a stream-oriented socket
int serverSd = socket(AF_INET, SOCK_STREAM, 0);
// Signal OS to reuse this port once server closes
const int on = 1;
setsockopt(serverSd, SOL_SOCKET, SO_REUSEADDR, (char*)&on, sizeof(int));
// Bind socket to local address
bind(serverSd, (sockaddr*)&acceptSockAddr, sizeof(acceptSockAddr));
// Instruct OS to listen for up to 5 clients
listen(serverSd, 5);
// Declare a new socket
sockaddr_in newSockAddr;
socklen_t newSockAddrSize = sizeof(newSockAddr);
int newSd;
// Set up signal handler for IO from client
struct sigaction action;  
memset(&action, '', sizeof(action));
action.sa_sigaction = &readFromClient;
action.sa_flags = SA_SIGINFO;
//fcntl(newSd, F_SETSIG, SIGIO); // Fixes problem with si_fd
if(sigaction(SIGIO, &action, NULL) < 0)
{
perror("sigaction");
return 1;
}
// sleep forever
cout << "Sleeping..." << endl;
while(1)
{
cout << "Waiting for client... " << endl;
newSd = accept(serverSd, (sockaddr*)&newSockAddr, &newSockAddrSize);
cout << "SUCCESS" << endl;
cout << "Switching to asynchronous communication... " << endl;
fcntl(newSd, F_SETOWN, getpid());
fcntl(newSd, F_SETFL, FASYNC);
cout << "SUCCESS" << endl;
cout << "Resuming sleep... " << endl;
sleep(10);
}
return 0;
}

这是我目前为客户提供的代码：

#include <sys/types.h>    // socket, bind
#include <sys/socket.h>   // socket, bind, listen, inet_ntoa
#include <netinet/in.h>   // htonl, htons, inet_ntoa
#include <arpa/inet.h>    // inet_ntoa
#include <netdb.h>        // gethostbyname
#include <unistd.h>       // read, write, close
#include <string.h>       // bzero
#include <netinet/tcp.h>  // SO_REUSEADDR
#include <sys/uio.h>      // writev
#include <signal.h>       // sigaction
#include <sys/time.h>     // gettimeofday
#include <unistd.h>       // write
#include <fcntl.h>        // fcntl
#include <iostream>       // cout
using namespace std;
#define BUFSIZE 1500
#define SIZEOFINT 4
int main(int argc, char *argv[])
{
cout << "Client is running!" << endl;
// Store commmand line arguments
int server_port = atoi(argv[1]);
int nreps = atoi(argv[2]);
int nbufs = atoi(argv[3]);
int bufsize = atoi(argv[4]);
const char* server_name = argv[5];
int testType = atoi(argv[6]);
cout << "server_port: " << server_port << endl;
cout << "nreps: " << nreps << endl;
cout << "nbufs: " << nbufs << endl;
cout << "bufsize: " << bufsize << endl;
cout << "server_name: " << server_name << endl;
cout << "testType: " << testType << endl;
// Check to ensure proper buffer count/sizes
if(nbufs * bufsize != BUFSIZE)
{
cout << "nbufs times bufsize must equal " << BUFSIZE << endl;
exit(0);
}
if(testType < 1 || testType > 3)
{
cout << "test type must be 1, 2, or 3" << endl;
exit(0);
}
// Create buffers
char databuf[nbufs][bufsize];
// Retrieve hostent structure
struct hostent* host = gethostbyname(server_name);
// Declare socket structure
sockaddr_in sendSockAddr;
memset((char*)&sendSockAddr, '', sizeof(sendSockAddr));
sendSockAddr.sin_family = AF_INET; // Address Family Internet
sendSockAddr.sin_addr.s_addr = inet_addr(inet_ntoa(*(struct in_addr*)*host->h_addr_list));
sendSockAddr.sin_port = htons(server_port);  // convert host byte-order
// Open stream-oriented socket
int clientSd = socket(AF_INET, SOCK_STREAM, 0);
// Connect socket to server
cout << "Connecting socket to server... " << endl;
int code = connect(clientSd, (sockaddr*)&sendSockAddr, sizeof(sendSockAddr));
cout << "Connection result: " << code << endl;
// Record start time
struct timeval theTime;
gettimeofday(&theTime, NULL);
int startTime = theTime.tv_usec + theTime.tv_sec * 1000000;
// Conduct tests
for(int i = 0; i < nreps; i++)
{
switch(testType)
{
case 1:
{
// Multiple write test
cout << "Running multiple write test" << endl;
for(int j = 0; j < nbufs; j++)
{
cout << "Writing buffer " << j << "... " << endl;
write(clientSd, databuf[j], bufsize);
cout << "SUCCESS" << endl;
}
cout << "Finished multiple write test" << endl;
}
case 2:
{
// Vector write test
cout << "Running vector write test" << endl;
struct iovec vector[nbufs];
for(int j = 0; j < nbufs; j++)
{
vector[j].iov_base = databuf[j];
vector[j].iov_len = bufsize;
}
cout << "Writing vector... " << endl;
writev(clientSd, vector, nbufs);
cout << "SUCCESS" << endl;
cout << "Finished vector write test" << endl;
}
case 3:
{
// Single write test
cout << "Running single write test" << endl;
/*
cout << "Writing... ";
write(clientSd, databuf, nbufs * bufsize);
cout << "SUCCESS" << endl;
*/
// For testing single byte write
cout << "writing a byte..." << endl;
char singleByte[1];
write(clientSd, singleByte, 1);
cout << "wrote a byte!" << endl;
cout << "Finished single write test" << endl;
}
}
}
// Record finish time
gettimeofday(&theTime, NULL);
int finishTime = theTime.tv_usec + theTime.tv_sec * 1000000;
// Calculate the sending time
int sendTime = finishTime - startTime;
// Receive number of bytes read from server
int nReads;
cout << "reading nReads from server... " << endl;
read(clientSd, (void*)nReads, SIZEOFINT);
cout << "SUCCESS" << endl;
// Record read time
gettimeofday(&theTime, NULL);
int readTime = theTime.tv_usec + theTime.tv_sec * 1000000;
// Calculate the round-trip time
int roundTime = readTime - startTime;
// Display data sending statistics
cout << "Test " << testType << ": data-sending time = " << sendTime;
cout << " usec, round-trip time = " << roundTime << " usec, # reads = ";
cout << nReads << endl;
// Close the socket
cout << "Closing the socket... " << endl;
close(clientSd);
cout << "SUCCESS" << endl;
cout << "Exiting!" << endl;
return 0;
}

我已经花了大约14个小时来解决这个问题，在来这里之前尝试了很多东西：

• 使用SIGTERM而不是SIGIO
• 重新安排操作顺序，以便在接受传入连接之前设置sigaction
• 在触发函数中使用fcntl，而不是在睡眠循环中使用
• 使用传递给触发函数的siginfo_t结构中的字段描述符
• 使用sa_handler而不是设置sa_sginfo的标志(因此不会传递siginfo_t)
• 根本不调用fcntl
• 切换运行这些程序的服务器
• 切换这些程序正在使用的端口
• 在睡眠循环之前调用所有内容

在这一点上，我的导师告诉我使用不推荐使用的信号方法，但这似乎是一个糟糕的解决方案。当然，siginfo现在是一种常见的做法，使用它不应该那么困难吗？任何关于尝试的建议都将不胜感激！