socket编程中recv与send函数

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socket编程中recv与send函数

2024-07-04 04:05:35 230人阅读

recv函数会将套接字缓冲区中的内容读出，但不清空，与read函数的区别在此。此函数有一个flag标志位，设为MSG_PEEK。

send函数会将缓冲区中的内容写入到套接字，也不清空，与write函数的区别在此。

用这两个函数可以先接收或发送缓冲区中的内容，然后再用readn（此时缓冲区中的内容依然存在）与write函数去继续判断换行符/n，对缓冲区内容实现换行输出。

echocli.c

#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>

#define ERR_EXIT(m) \
        do \
        { \
                perror(m); \
                exit(EXIT_FAILURE); \
        } while(0)

ssize_t readn(int fd, void *buf, size_t count)
{
        size_t nleft = count;
        ssize_t nread;
        char *bufp = (char*)buf;

        while (nleft > 0)
        {
                if ((nread = read(fd, bufp, nleft)) < 0)
                {
                        if (errno == EINTR)
                                continue;
                        return -1;
                }
                else if (nread == 0)
                        return count - nleft;

                bufp += nread;
                nleft -= nread;
        }

        return count;
}

ssize_t writen(int fd, const void *buf, size_t count)
{
        size_t nleft = count;
        ssize_t nwritten;
        char *bufp = (char*)buf;

        while (nleft > 0)
        {
                if ((nwritten = write(fd, bufp, nleft)) < 0)
                {
                        if (errno == EINTR)
                                continue;
                        return -1;
                }
                else if (nwritten == 0)
                        continue;

                bufp += nwritten;
                nleft -= nwritten;
        }

        return count;
}

ssize_t recv_peek(int sockfd, void *buf, size_t len)
{
        while (1)
        {
                int ret = recv(sockfd, buf, len, MSG_PEEK);
                if (ret == -1 && errno == EINTR)
                        continue;
                return ret;
        }
}

ssize_t readline(int sockfd, void *buf, size_t maxline)
{
        int ret;
        int nread;
        char *bufp = buf;
        int nleft = maxline;
        while (1)
        {
                ret = recv_peek(sockfd, bufp, nleft);
                if (ret < 0)
                        return ret;
                else if (ret == 0)
                        return ret;

                nread = ret;
                int i;
                for (i=0; i<nread; i++)
                {
                        if (bufp[i] == ‘\n‘)
                        {
                                ret = readn(sockfd, bufp, i+1);
                                if (ret != i+1)
                                        exit(EXIT_FAILURE);

                                return ret;
                        }
                }

                if (nread > nleft)
                        exit(EXIT_FAILURE);

                nleft -= nread;
                ret = readn(sockfd, bufp, nread);
                if (ret != nread)
                        exit(EXIT_FAILURE);

                bufp += nread;
        }

        return -1;
}

void echo_cli(int sock)
{
   char sendbuf[1024] = {0};
        char recvbuf[1024] = {0};
        while (fgets(sendbuf, sizeof(sendbuf), stdin) != NULL)
        {
                writen(sock, sendbuf, strlen(sendbuf));

                int ret = readline(sock, recvbuf, sizeof(recvbuf));
                if (ret == -1)
                        ERR_EXIT("readline");
                else if (ret == 0)
                {
                        printf("client close\n");
                        break;
                }

                fputs(recvbuf, stdout);
                memset(sendbuf, 0, sizeof(sendbuf));
                memset(recvbuf, 0, sizeof(recvbuf));
        }

        close(sock);
}

int main(void)
{
   int sock;
   if ((sock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
       ERR_EXIT("socket");

   struct sockaddr_in servaddr;
   memset(&servaddr, 0, sizeof(servaddr));
   servaddr.sin_family = AF_INET;
   servaddr.sin_port = htons(5188);
   servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");

   if (connect(sock, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0)
       ERR_EXIT("connect");

   struct sockaddr_in localaddr;
   socklen_t addrlen = sizeof(localaddr);
   if (getsockname(sock, (struct sockaddr*)&localaddr, &addrlen) < 0)
       ERR_EXIT("getsockname");

   printf("ip=%s port=%d\n", inet_ntoa(localaddr.sin_addr), ntohs(localaddr.sin_port));

   echo_cli(sock);

   return 0;
}

echosrv.c

#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <signal.h>
#include <sys/wait.h>

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>

#define ERR_EXIT(m) \
        do \
        { \
                perror(m); \
                exit(EXIT_FAILURE); \
        } while(0)

ssize_t readn(int fd, void *buf, size_t count)
{
   size_t nleft = count;
   ssize_t nread;
   char *bufp = (char*)buf;

   while (nleft > 0)
   {
       if ((nread = read(fd, bufp, nleft)) < 0)
       {
           if (errno == EINTR)
               continue;
           return -1;
       }
       else if (nread == 0)
           return count - nleft;

       bufp += nread;
       nleft -= nread;
   }

   return count;
}

ssize_t writen(int fd, const void *buf, size_t count)
{
   size_t nleft = count;
   ssize_t nwritten;
   char *bufp = (char*)buf;

   while (nleft > 0)
   {
       if ((nwritten = write(fd, bufp, nleft)) < 0)
       {
           if (errno == EINTR)
               continue;
           return -1;
       }
       else if (nwritten == 0)
           continue;

       bufp += nwritten;
       nleft -= nwritten;
   }

   return count;
}

ssize_t recv_peek(int sockfd, void *buf, size_t len)
{
   while (1)
   {
       int ret = recv(sockfd, buf, len, MSG_PEEK);
       if (ret == -1 && errno == EINTR)
           continue;
       return ret;
   }
}

ssize_t readline(int sockfd, void *buf, size_t maxline)
{
   int ret;
   int nread;
   char *bufp = buf;
   int nleft = maxline;
   while (1)
   {
       ret = recv_peek(sockfd, bufp, nleft);
       if (ret < 0)
           return ret;
       else if (ret == 0)
           return ret;

       nread = ret;
       int i;
       for (i=0; i<nread; i++)
       {
           if (bufp[i] == ‘\n‘)
           {
               ret = readn(sockfd, bufp, i+1);
               if (ret != i+1)
                   exit(EXIT_FAILURE);

               return ret;
           }
       }

       if (nread > nleft)
           exit(EXIT_FAILURE);

       nleft -= nread;
       ret = readn(sockfd, bufp, nread);
       if (ret != nread)
           exit(EXIT_FAILURE);

       bufp += nread;
   }

   return -1;
}

void echo_srv(int conn)
{
   char recvbuf[1024];
        while (1)
        {
                memset(recvbuf, 0, sizeof(recvbuf));
                int ret = readline(conn, recvbuf, 1024);
       if (ret == -1)
           ERR_EXIT("readline");
       if (ret == 0)
       {
           printf("client close\n");
           break;
       }

                fputs(recvbuf, stdout);
                writen(conn, recvbuf, strlen(recvbuf));
        }
}

void handle_sigchld(int sig)
{
/*   wait(NULL);*/
   while (waitpid(-1, NULL, WNOHANG) > 0)
       ;
}

int main(void)
{
/*   signal(SIGCHLD, SIG_IGN);*/
   signal(SIGCHLD, handle_sigchld);
   int listenfd;
   if ((listenfd = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
/*   if ((listenfd = socket(PF_INET, SOCK_STREAM, 0)) < 0)*/
       ERR_EXIT("socket");

   struct sockaddr_in servaddr;
   memset(&servaddr, 0, sizeof(servaddr));
   servaddr.sin_family = AF_INET;
   servaddr.sin_port = htons(5188);
   servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
   /*servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");*/
   /*inet_aton("127.0.0.1", &servaddr.sin_addr);*/

   int on = 1;
   if (setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
       ERR_EXIT("setsockopt");

   if (bind(listenfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0)
       ERR_EXIT("bind");
   if (listen(listenfd, SOMAXCONN) < 0)
       ERR_EXIT("listen");

   struct sockaddr_in peeraddr;
   socklen_t peerlen = sizeof(peeraddr);
   int conn;

   pid_t pid;
   while (1)
   {
       if ((conn = accept(listenfd, (struct sockaddr*)&peeraddr, &peerlen)) < 0)
           ERR_EXIT("accept");

       printf("ip=%s port=%d\n", inet_ntoa(peeraddr.sin_addr), ntohs(peeraddr.sin_port));

       pid = fork();
       if (pid == -1)
           ERR_EXIT("fork");
       if (pid == 0)
       {
           close(listenfd);
           echo_srv(conn);
           exit(EXIT_SUCCESS);
       }
       else
           close(conn);
   }

   return 0;
}

echocli2.c

#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>

#define ERR_EXIT(m) \
        do \
        { \
                perror(m); \
                exit(EXIT_FAILURE); \
        } while(0)

ssize_t readn(int fd, void *buf, size_t count)
{
        size_t nleft = count;
        ssize_t nread;
        char *bufp = (char*)buf;

        while (nleft > 0)
        {
                if ((nread = read(fd, bufp, nleft)) < 0)
                {
                        if (errno == EINTR)
                                continue;
                        return -1;
                }
                else if (nread == 0)
                        return count - nleft;

                bufp += nread;
                nleft -= nread;
        }

        return count;
}

ssize_t writen(int fd, const void *buf, size_t count)
{
        size_t nleft = count;
        ssize_t nwritten;
        char *bufp = (char*)buf;

        while (nleft > 0)
        {
                if ((nwritten = write(fd, bufp, nleft)) < 0)
                {
                        if (errno == EINTR)
                                continue;
                        return -1;
                }
                else if (nwritten == 0)
                        continue;

                bufp += nwritten;
                nleft -= nwritten;
        }

        return count;
}

ssize_t recv_peek(int sockfd, void *buf, size_t len)
{
        while (1)
        {
                int ret = recv(sockfd, buf, len, MSG_PEEK);
                if (ret == -1 && errno == EINTR)
                        continue;
                return ret;
        }
}

ssize_t readline(int sockfd, void *buf, size_t maxline)
{
        int ret;
        int nread;
        char *bufp = buf;
        int nleft = maxline;
        while (1)
        {
                ret = recv_peek(sockfd, bufp, nleft);
                if (ret < 0)
                        return ret;
                else if (ret == 0)
                        return ret;

                nread = ret;
                int i;
                for (i=0; i<nread; i++)
                {
                        if (bufp[i] == ‘\n‘)
                        {
                                ret = readn(sockfd, bufp, i+1);
                                if (ret != i+1)
                                        exit(EXIT_FAILURE);

                                return ret;
                        }
                }

                if (nread > nleft)
                        exit(EXIT_FAILURE);

                nleft -= nread;
                ret = readn(sockfd, bufp, nread);
                if (ret != nread)
                        exit(EXIT_FAILURE);

                bufp += nread;
        }

        return -1;
}

void echo_cli(int sock)
{
   char sendbuf[1024] = {0};
        char recvbuf[1024] = {0};
        while (fgets(sendbuf, sizeof(sendbuf), stdin) != NULL)
        {
                writen(sock, sendbuf, strlen(sendbuf));

                int ret = readline(sock, recvbuf, sizeof(recvbuf));
                if (ret == -1)
                        ERR_EXIT("readline");
                else if (ret == 0)
                {
                        printf("client close\n");
                        break;
                }

                fputs(recvbuf, stdout);
                memset(sendbuf, 0, sizeof(sendbuf));
                memset(recvbuf, 0, sizeof(recvbuf));
        }

        close(sock);
}

int main(void)
{
   int sock[5];
   int i;
   for (i=0; i<5; i++)
   {
       if ((sock[i] = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
           ERR_EXIT("socket");

       struct sockaddr_in servaddr;
       memset(&servaddr, 0, sizeof(servaddr));
       servaddr.sin_family = AF_INET;
       servaddr.sin_port = htons(5188);
       servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");

       if (connect(sock[i], (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0)
           ERR_EXIT("connect");

       struct sockaddr_in localaddr;
       socklen_t addrlen = sizeof(localaddr);
       if (getsockname(sock[i], (struct sockaddr*)&localaddr, &addrlen) < 0)
           ERR_EXIT("getsockname");

       printf("ip=%s port=%d\n", inet_ntoa(localaddr.sin_addr), ntohs(localaddr.sin_port));
   }

   echo_cli(sock[0]);

   return 0;
}

makefile:

.PHONY:clean all
CC=gcc
CFLAGS=-Wall -g
BIN=echosrv echocli echocli2
all:$(BIN)
%.o:%.c
$(CC) $(CFLAGS) -c $< -o $@
clean:
rm -f *.o $(BIN)

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socket编程中recv与send函数

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