下面的代码来自IBM学习网站，是学习socket通信和select使用的一个很好的源码。
server.c 服务器端
#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> #define SERVER_PORT 12345 #define TRUE 1
#define FALSE 0 main (int argc, char *argv[])
{
int i, len, rc, on = ;
int listen_sd, max_sd, new_sd;
int desc_ready, end_server = FALSE;
int close_conn;
char buffer[];
struct sockaddr_in addr;
struct timeval timeout;
fd_set master_set, working_set; /*************************************************************/
/* Create an AF_INET stream socket to receive incoming */
/* connections on */
/*************************************************************/
listen_sd = socket(AF_INET, SOCK_STREAM, );
if (listen_sd < )
{
perror("socket() failed");
exit(-);
} /*************************************************************/
/* Allow socket descriptor to be reuseable */
/*************************************************************/
rc = setsockopt(listen_sd, SOL_SOCKET, SO_REUSEADDR,
(char *)&on, sizeof(on));
if (rc < )
{
perror("setsockopt() failed");
close(listen_sd);
exit(-);
} /*************************************************************/
/* Set socket to be non-blocking. All of the sockets for */
/* the incoming connections will also be non-blocking since */
/* they will inherit that state from the listening socket. */
/*************************************************************/
rc = ioctl(listen_sd, FIONBIO, (char *)&on);
if (rc < )
{
perror("ioctl() failed");
close(listen_sd);
exit(-);
} /*************************************************************/
/* Bind the socket */
/*************************************************************/
memset(&addr, , sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = htonl(INADDR_ANY);
addr.sin_port = htons(SERVER_PORT);
rc = bind(listen_sd,
(struct sockaddr *)&addr, sizeof(addr));
if (rc < )
{
perror("bind() failed");
close(listen_sd);
exit(-);
} /*************************************************************/
/* Set the listen back log */
/*************************************************************/
rc = listen(listen_sd, );
if (rc < )
{
perror("listen() failed");
close(listen_sd);
exit(-);
} /*************************************************************/
/* Initialize the master fd_set */
/*************************************************************/
FD_ZERO(&master_set);
max_sd = listen_sd;
FD_SET(listen_sd, &master_set); /*************************************************************/
/* Initialize the timeval struct to 3 minutes. If no */
/* activity after 3 minutes this program will end. */
/*************************************************************/
timeout.tv_sec = * ;
timeout.tv_usec = ; /*************************************************************/
/* Loop waiting for incoming connects or for incoming data */
/* on any of the connected sockets. */
/*************************************************************/
do
{
/**********************************************************/
/* Copy the master fd_set over to the working fd_set. */
/**********************************************************/
memcpy(&working_set, &master_set, sizeof(master_set)); /**********************************************************/
/* Call select() and wait 5 minutes for it to complete. */
/**********************************************************/
printf("listen_sd is %d ",listen_sd);
printf("Waiting on select()...\n"); rc = select(max_sd + , &working_set, NULL, NULL, &timeout); /**********************************************************/
/* Check to see if the select call failed. */
/**********************************************************/
if (rc < )
{
perror(" select() failed");
break;
} /**********************************************************/
/* Check to see if the 5 minute time out expired. */
/**********************************************************/
if (rc == )
{
printf(" select() timed out. End program.\n");
break;
} /**********************************************************/
/* One or more descriptors are readable. Need to */
/* determine which ones they are. */
/**********************************************************/
desc_ready = rc;
for (i=; i <= max_sd && desc_ready > ; ++i)
{
/*******************************************************/
/* Check to see if this descriptor is ready */
/*******************************************************/
if (FD_ISSET(i, &working_set))
{
/****************************************************/
/* A descriptor was found that was readable - one */
/* less has to be looked for. This is being done */
/* so that we can stop looking at the working set */
/* once we have found all of the descriptors that */
/* were ready. */
/****************************************************/
desc_ready -= ; /****************************************************/
/* Check to see if this is the listening socket */
/****************************************************/
if (i == listen_sd)
{
printf(" Listening socket is readable\n");
/*************************************************/
/* Accept all incoming connections that are */
/* queued up on the listening socket before we */
/* loop back and call select again. */
/*************************************************/
do
{
/**********************************************/
/* Accept each incoming connection. If */
/* accept fails with EWOULDBLOCK, then we */
/* have accepted all of them. Any other */
/* failure on accept will cause us to end the */
/* server. */
/**********************************************/
new_sd = accept(listen_sd, NULL, NULL);
if (new_sd < )
{
if (errno != EWOULDBLOCK)
{
perror(" accept() failed");
end_server = TRUE;
}
break;
} /**********************************************/
/* Add the new incoming connection to the */
/* master read set */
/**********************************************/
printf(" New incoming connection - %d\n", new_sd);
FD_SET(new_sd, &master_set);
if (new_sd > max_sd)
max_sd = new_sd; /**********************************************/
/* Loop back up and accept another incoming */
/* connection */
/**********************************************/
} while (new_sd != -);
} /****************************************************/
/* This is not the listening socket, therefore an */
/* existing connection must be readable */
/****************************************************/
else
{
printf(" Descriptor %d is readable\n", i);
close_conn = FALSE;
/*************************************************/
/* Receive all incoming data on this socket */
/* before we loop back and call select again. */
/*************************************************/
do
{
/**********************************************/
/* Receive data on this connection until the */
/* recv fails with EWOULDBLOCK. If any other */
/* failure occurs, we will close the */
/* connection. */
/**********************************************/
rc = recv(i, buffer, sizeof(buffer), );
if (rc < )
{
if (errno != EWOULDBLOCK)
{
perror(" recv() failed");
close_conn = TRUE;
}
break;
} /**********************************************/
/* Check to see if the connection has been */
/* closed by the client */
/**********************************************/
if (rc == )
{
printf(" Connection closed\n");
close_conn = TRUE;
break;
} /**********************************************/
/* Data was recevied */
/**********************************************/
len = rc;
printf(" %d bytes received\n", len); /**********************************************/
/* Echo the data back to the client */
/**********************************************/
rc = send(i, buffer, len, );
if (rc < )
{
perror(" send() failed");
close_conn = TRUE;
break;
} } while (TRUE); /*************************************************/
/* If the close_conn flag was turned on, we need */
/* to clean up this active connection. This */
/* clean up process includes removing the */
/* descriptor from the master set and */
/* determining the new maximum descriptor value */
/* based on the bits that are still turned on in */
/* the master set. */
/*************************************************/
if (close_conn)
{
close(i);
FD_CLR(i, &master_set);
if (i == max_sd)
{
while (FD_ISSET(max_sd, &master_set) == FALSE)
max_sd -= ;
}
}
} /* End of existing connection is readable */
} /* End of if (FD_ISSET(i, &working_set)) */
} /* End of loop through selectable descriptors */ } while (end_server == FALSE); /*************************************************************/
/* Cleanup all of the sockets that are open */
/*************************************************************/
for (i=; i <= max_sd; ++i)
{
if (FD_ISSET(i, &master_set))
close(i);
}
}
client.c 客户端
/**************************************************************************/
/* Generic client example is used with connection-oriented server designs */
/**************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h> #define SERVER_PORT 12345 main (int argc, char *argv[])
{
int len, rc;
int sockfd;
char send_buf[];
char recv_buf[];
struct sockaddr_in addr; /*************************************************/
/* Create an AF_INET stream socket */
/*************************************************/
sockfd = socket(AF_INET, SOCK_STREAM, );
if (sockfd < )
{
perror("socket");
exit(-);
} /*************************************************/
/* Initialize the socket address structure */
/*************************************************/
memset(&addr, , sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = htonl(INADDR_ANY);
addr.sin_port = htons(SERVER_PORT); /*************************************************/
/* Connect to the server */
/*************************************************/
rc = connect(sockfd,
(struct sockaddr *)&addr,
sizeof(struct sockaddr_in));
if (rc < )
{
perror("connect");
close(sockfd);
exit(-);
}
printf("Connect completed.socketfd is %d .rc is %d \n",sockfd,rc); /*************************************************/
/* Enter data buffer that is to be sent */
/*************************************************/
printf("Enter message to be sent:\n");
gets(send_buf); /*************************************************/
/* Send data buffer to the worker job */
/*************************************************/
len = send(sockfd, send_buf, strlen(send_buf) + , );
if (len != strlen(send_buf) + )
{
perror("send");
close(sockfd);
exit(-);
}
printf("%d bytes sent\n", len); /*************************************************/
/* Receive data buffer from the worker job */
/*************************************************/
len = recv(sockfd, recv_buf, sizeof(recv_buf), );
if (len != strlen(send_buf) + )
{
perror("recv");
close(sockfd);
exit(-);
}
printf("%d bytes received\n", len); /*************************************************/
/* Close down the socket */
/*************************************************/
close(sockfd);
}