socket编程例子
客户端例子：
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <malloc.h>
#include <netdb.h>
#include <fcntl.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#define RES_LENGTH 10240 //接受字符的最大长度
int connect_socket(char * server,int serverPort);
int send_msg(int sockfd,char * sendBuff);
char * recv_msg(int sockfd);
int close_socket(int sockfd);
int main(int argc, char ** argv)
{
int sockfd=0;
char sendMsg[30]="abc.org\r\n\r";
char* res;
int port = 4242;
char ip[128] = {0};
strncpy(ip, "127.0.0.1", 128);
if(argc > 2)
{
strncpy(ip, argv[1], 128);
port = atoi(argv[2]);
printf("Input IP: %s, port : %d\n", ip, port);
}
else if(argc > 1)
{
port = atoi(argv[1]);
printf("Input port : %d\n", port);
}
sockfd=connect_socket(ip, port);
send_msg(sockfd,sendMsg);
/* res=recv_msg(sockfd); */
printf("return from recv function\n");
printf(res);
free(res);
close_socket(sockfd);
return 0;
}
/************************************************************
* 连接SOCKET服务器，如果出错返回-1，否则返回socket处理代码
* server：服务器地址(域名或者IP),serverport：端口
* ********************************************************/
int connect_socket(char * server,int serverPort){
int sockfd=0;
struct sockaddr_in addr;
struct hostent * phost;
//向系统注册，通知系统建立一个通信端口
//AF_INET表示使用IPv4协议
//SOCK_STREAM表示使用TCP协议
if((sockfd=socket(AF_INET,SOCK_STREAM,0))<0){
herror("Init socket error!");
return -1;
}
bzero(&addr,sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(serverPort);
addr.sin_addr.s_addr = inet_addr(server);//按IP初始化
if(addr.sin_addr.s_addr == INADDR_NONE){//如果输入的是域名
phost = (struct hostent*)gethostbyname(server);
if(phost==NULL){
herror("Init socket s_addr error!");
return -1;
}
addr.sin_addr.s_addr =((struct in_addr*)phost->h_addr)->s_addr;
}
if(connect(sockfd,(struct sockaddr*)&addr, sizeof(addr))<0)
{
perror("Connect server fail!");
return -1; //0表示成功，-1表示失败
}
else
return sockfd;
}
/**************************************************************
* 发送消息，如果出错返回-1，否则返回发送的字符长度
* sockfd：socket标识，sendBuff：发送的字符串
* *********************************************************/
int send_msg(int sockfd,char * sendBuff)
{
int sendSize=0;
if((sendSize=send(sockfd,sendBuff,strlen(sendBuff),0))<=0){
herror("Send msg error!");
return -1;
}else
return sendSize;
}
/****************************************************************
*接受消息，如果出错返回NULL，否则返回接受字符串的指针(动态分配，注意释放)
*sockfd：socket标识
* *********************************************************/
char* recv_msg(int sockfd){
char * response;
int flag=0,recLenth=0;
response=(char *)malloc(RES_LENGTH);
memset(response,0,RES_LENGTH);
for(flag=0;;)
{
printf("======recv data:\n");
if(( recLenth=recv(sockfd,response+flag,RES_LENGTH-flag,0))==-1 )
{
free(response);
printf("Return value : %d\n", recLenth);
perror("Recv msg error : ");
return NULL;
}
else if(recLenth==0)
break;
else
{
printf("%d char recieved data : %s.\n", recLenth, response+flag);
flag+=recLenth;
recLenth=0;
}
}
printf("Return value : %d\n", recLenth);
response[flag]='\0';
return response;
}
/**************************************************
*关闭连接
* **********************************************/
int close_socket(int sockfd)
{
close(sockfd);
return 0;
}
tcp服务端例子：
#include <unistd.h> /* fork, close */
#include <stdlib.h> /* exit */
#include <string.h> /* strlen */
#include <stdio.h> /* perror, fdopen, fgets */
#include <sys/socket.h>
#include <sys/wait.h> /* waitpid */
#include <netdb.h> /* getaddrinfo */
#define die(msg) do { perror(msg); exit(EXIT_FAILURE); } while (0)
#define PORT "4242"
#define NUM_CHILDREN 3
#define MAXLEN 1024
int readline(int fd, char *buf, int maxlen); // forward declaration
int recvdata(int fd, char *buf, int maxlen); // forward declaration
int main(int argc, char** argv)
{
int i, n, sockfd, clientfd;
int yes = 1; // used in setsockopt(2)
struct addrinfo *ai;
struct sockaddr_in *client;
socklen_t client_t;
pid_t cpid; // child pid
char line[MAXLEN];
char cpid_s[32];
char welcome[32];
/* Create a socket and get its file descriptor -- socket(2) */
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd == -1) {
die("Couldn't create a socket");
}
/* Prevents those dreaded "Address already in use" errors */
if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, (const void *)&yes, sizeof(int)) == -1) {
die("Couldn't setsockopt");
}
/* Fill the address info struct (host + port) -- getaddrinfo(3) */
if (getaddrinfo(NULL, PORT, NULL, &ai) != 0) { // get localhost
die("Couldn't get address");
}
/* Assign address to this socket's fd */
if (bind(sockfd, ai->ai_addr, ai->ai_addrlen) != 0) { // only bind on localhost ip
die("Couldn't bind socket to address");
}
/* Free the memory used by our address info struct */
freeaddrinfo(ai);
/* Mark this socket as able to accept incoming connections */
/* printf("Process %d Listening\n", getpid()); */
if (listen(sockfd, 10) == -1) {
die("Couldn't make socket listen");
}
printf("One new connection is coming!\n");
/* Fork you some child processes. */
for (i = 0; i < NUM_CHILDREN; i++) {
cpid = fork();
if (cpid == -1) {
die("Couldn't fork");
}
if (cpid == 0) { // We're in the child ...
for (;;) { // Run forever ...
/* Necessary initialization for accept(2) */
client_t = sizeof client;
/* Blocks! */
printf("Waiting new connection!\n");
clientfd = accept(sockfd, (struct sockaddr *)&client, &client_t);
if (clientfd == -1) {
die("Couldn't accept a connection");
}
/* Send a welcome message/prompt */
bzero(cpid_s, 32);
bzero(welcome, 32);
sprintf(cpid_s, "%d", getpid());
sprintf(welcome, "Child %s echo> ", cpid_s);
send(clientfd, welcome, strlen(welcome), 0);
/* Read a line from the client socket ... */
/* n = readline(clientfd, line, MAXLEN);
if (n == -1) {
die("Couldn't read line from connection");
} */
n = recvdata(clientfd, line, MAXLEN);
printf("recieve data: %s", line);
/* ... and echo it back */
send(clientfd, line, n, 0);
/* Clean up the client socket */
close(clientfd);
printf("Close client socket.\n");
}
}
}
/* Sit back and wait for all child processes to exit */
while (waitpid(-1, NULL, 0) > 0);
/* Close up our socket */
close(sockfd);
printf("Close server socket.\n");
return 0;
}
/**
* Simple utility function that reads a line from a file descriptor fd,
* up to maxlen bytes -- ripped from Unix Network Programming, Stevens.
*/
int readline(int fd, char *buf, int maxlen)
{
int n, rc;
char c;
for (n = 1; n < maxlen; n++) {
if ((rc = read(fd, &c, 1)) == 1) {
*buf++ = c;
if (c == '\n')
break;
} else if (rc == 0) {
if (n == 1)
return 0; // EOF, no data read
else
break; // EOF, read some data
} else
return -1; // error
}
*buf = '\0'; // null-terminate
return n;
}
int recvdata(int fd, char *buf, int maxlen)
{
return recv(fd, buf, maxlen, 0);
}
采用Select的TCP Server:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#define MYPORT 1234 // the port users will be connecting to
#define BACKLOG 5 // how many pending connections queue will hold
#define BUF_SIZE 1024
int fd_A[BACKLOG]; // accepted connection fd
int conn_amount; // current connection amount
void showclient()
{
int i;
printf("client amount: %d\n", conn_amount);
for (i = 0; i < BACKLOG; i++) {
printf("[%d]:%d ", i, fd_A[i]);
}
printf("\n\n");
}
int main(void)
{
int sock_fd, new_fd; // listen on sock_fd, new connection on new_fd
struct sockaddr_in server_addr; // server address information
struct sockaddr_in client_addr; // connector's address information
socklen_t sin_size;
int yes = 1;
char buf[BUF_SIZE];
int ret;
int i;
if ((sock_fd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
perror("socket");
exit(1);
}
if (setsockopt(sock_fd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int)) == -1) {
perror("setsockopt");
exit(1);
}
server_addr.sin_family = AF_INET; // host byte order
server_addr.sin_port = htons(MYPORT); // short, network byte order
server_addr.sin_addr.s_addr = INADDR_ANY; // automatically fill with my IP
memset(server_addr.sin_zero, '\0', sizeof(server_addr.sin_zero));
if (bind(sock_fd, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) {
perror("bind");
exit(1);
}
if (listen(sock_fd, BACKLOG) == -1) {
perror("listen");
exit(1);
}
printf("listen port %d\n", MYPORT);
fd_set fdsr;
int maxsock;
struct timeval tv;
conn_amount = 0;
sin_size = sizeof(client_addr);
maxsock = sock_fd;
while (1)
{
// initialize file descriptor set
FD_ZERO(&fdsr);
FD_SET(sock_fd, &fdsr); // add fd
// timeout setting
tv.tv_sec = 30;
tv.tv_usec = 0;
// add active connection to fd set
for (i = 0; i < BACKLOG; i++) {
if (fd_A[i] != 0) {
FD_SET(fd_A[i], &fdsr);
}
}
ret = select(maxsock + 1, &fdsr, NULL, NULL, &tv);
if (ret < 0) { // error
perror("select");
break;
} else if (ret == 0) { // time out
printf("timeout\n");
continue;
}
// check every fd in the set
for (i = 0; i < conn_amount; i++)
{
if (FD_ISSET(fd_A[i], &fdsr)) // check which fd is ready
{
ret = recv(fd_A[i], buf, sizeof(buf), 0);
if (ret <= 0)
{ // client close
printf("ret : %d and client[%d] close\n", ret, i);
close(fd_A[i]);
FD_CLR(fd_A[i], &fdsr); // delete fd
fd_A[i] = 0;
conn_amount--;
}
else
{ // receive data
if (ret < BUF_SIZE)
memset(&buf[ret], '\0', 1); // add NULL('\0')
printf("client[%d] send:%s\n", i, buf);
}
}
}
// check whether a new connection comes
if (FD_ISSET(sock_fd, &fdsr)) // accept new connection
{
new_fd = accept(sock_fd, (struct sockaddr *)&client_addr, &sin_size);
if (new_fd <= 0)
{
perror("accept");
continue;
}
// add to fd queue
if (conn_amount < BACKLOG)
{
fd_A[conn_amount++] = new_fd;
printf("new connection client[%d] %s:%d\n", conn_amount,
inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));
if (new_fd > maxsock) // update the maxsock fd for select function
maxsock = new_fd;
}
else
{
printf("max connections arrive, exit\n");
send(new_fd, "bye", 4, 0);
close(new_fd);
break;
}
}
showclient();
}
// close other connections
for (i = 0; i < BACKLOG; i++)
{
if (fd_A[i] != 0)
{
close(fd_A[i]);
}
}
exit(0);
}