C语言写了一个socket client端，适合windows和linux，用GCC编译运行通过

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　　///////////////////////////////////////////////////////////////////////////////
/*
gcc -Wall -o c1 c1.c -lws2_32
*/
///////////////////////////////////////////////////////////////////////////////
　　#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
　　#define _WIN32_WINNT  0x501
#define PORT 4000
#define IP_ADDRESS "127.0.0.1"
///////////////////////////////////////////////////////////////////////////////
// SK
　　#ifdef _WIN32_WINNT
#include <ws2tcpip.h>
#include <winsock2.h>
#else
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/un.h>
#include <netdb.h>
#endif
　　///////////////////////////////////////////////////////////////////////////////
// SK
　　void connect_inet_socket( int *psockfd, const char* host, int port );
　　#ifdef  _WIN32_WINNT
void connect_windows_socket( int *psockfd, const char* pathname );
#else
void connect_unix_socket( int *psockfd, const char* pathname );
#endif
　　void writebuffer_socket( int sockfd, const void *data, int len );
void readbuffer_socket( int sockfd, void *data, int len );
void shutdown_socket( int sockfd );
　　///////////////////////////////////////////////////////////////////////////////
// SK
/* Access to sockets needs to be done with a wrapper function 'connect_socket'
   and it is substituted by 'connect_windows_socket' or by 'connect_unix_socket'
   ( depends on a state of the macro  _WIN32 ) during preprocessing phase of
   the compilation.
   For portability 'connect_windows_socket' and 'connect_unix_socket' shouldn't
   be used directly and the wrapper function 'connect_socket' must be used instead.
*/
　　#ifdef  _WIN32_WINNT
#define connect_socket   connect_windows_socket
#else
#define connect_socket   connect_unix_socket
#endif
　　int socket_desc;
struct sockaddr_in server;
　　///////////////////////////////////////////////////////////////////////////////
/* Opens an internet socket.
   
   Note that fortran passes an extra argument for the string length,
   but this is ignored here for C compatibility.
   
   Args:
   psockfd: The id of the socket that will be created.
   port: The port number for the socket to be created. Low numbers are
         often reserved for important channels, so use of numbers of 4
         or more digits is recommended.
   host: The name of the host server.
*/
　　void connect_inet_socket( int *psockfd, const char* host, int port )
{
  int sockfd, ai_err;
  
  // creates an internet socket
  
  // fetches information on the host      
  struct addrinfo hints, *res;  
  char service[256];
  
  memset(&hints, 0, sizeof(hints));
  hints.ai_socktype = SOCK_STREAM;
  hints.ai_family = AF_UNSPEC;
  hints.ai_flags = AI_PASSIVE;
  
  //sprintf(service, "%d", port); // convert the port number to a string
  //ai_err = getaddrinfo(host, service, &hints, &res);
  //if (ai_err!=0) {
  //  printf("Error code: %i\n",ai_err);
  //  perror("Error fetching host data. Wrong host name?");
  //  exit(-1);
  //}
  
  // creates socket
  //sockfd = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
  sockfd = socket(AF_INET , SOCK_STREAM , IPPROTO_TCP);
  if (sockfd < 0) {
    perror("Error opening socket");
    exit(-1);
  }
  else
  {
  printf("creates socket:%d\n", sockfd);
  }
  
  // makes connection
  if (connect(sockfd, res->ai_addr, res->ai_addrlen) < 0) {
    perror("Error opening INET socket: wrong port or server unreachable");
    exit(-1);
  }
  freeaddrinfo(res);
  
  *psockfd = sockfd;
}
　　///////////////////////////////////////////////////////////////////////////////
// SK
/* Opens a socket.
   
   Note that fortran passes an extra argument for the string length,
   but this is ignored here for C compatibility.
   
   Args:
   psockfd: The id of the socket that will be created.
   pathname: The name of the file to use for sun_path.
*/
　　#ifdef  _WIN32_WINNT
　　void connect_windows_socket( int *psockfd, const char* pathname )
{
  // Required functionality for Windows
　　// ...
}
　　#else
　　void connect_unix_socket( int *psockfd, const char* pathname )
{
  // Required functionality for Unix
　　int sockfd, ai_err;
  
  struct sockaddr_in serv_addr;
  
  printf("Connecting to :%s:\n",pathname);
　　// fills up details of the socket addres
  memset(&serv_addr, 0, sizeof(serv_addr));
  serv_addr.sun_family = AF_UNIX;
  /* Beware of buffer over runs
     UNIX Network Programming by Richard Stevens mentions
     that the use of sizeof() is ok, but see
  http://mail-index.netbsd.org/tech-net/2006/10/11/0008.html
  */
  if ((int)strlen(pathname)> sizeof(serv_addr.sun_path)) {
    perror("Error opening UNIX socket: pathname too long\n");
    exit(-1);
  } else {     
    strcpy(serv_addr.sun_path, pathname);
  }
  // creates a unix socket
  
  // creates the socket
  sockfd = socket(AF_UNIX, SOCK_STREAM, 0);
  
  // connects
  if (connect(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) {
    perror("Error opening UNIX socket: path unavailable, or already existing");
    exit(-1);
  }
  *psockfd = sockfd;
}
　　#endif
　　///////////////////////////////////////////////////////////////////////////////
/* Writes to a socket.
　　Args:
   sockfd: The id of the socket that will be written to.
   data: The data to be written to the socket.
   len: The length of the data in bytes.
*/
　　void writebuffer_socket( int sockfd, const void *data, int len )
{
   int n;
　　n = write(sockfd, (char *) data, len);
   if (n < 0) {
     perror("Error writing to socket: server has quit or connection broke");
     exit(-1);
   }
}
　　///////////////////////////////////////////////////////////////////////////////
/* Reads from a socket.
　　Args:
   sockfd: The id of the socket that will be read from.
   data: The storage array for data read from the socket.
   len: The length of the data in bytes.
*/
　　void readbuffer_socket( int sockfd, void *data, int len )
{
   int n, nr;
   char *pdata;
　　pdata = (char *) data;
   n = nr = read(sockfd, pdata, len);
　　while (nr > 0 && n < len) {
     nr = read(sockfd, &(pdata[n]), len - n);
     n += nr;
   }
   if (n == 0) {
     perror("Error reading from socket: server has quit or connection broke");
     exit(-1);
   }
}
　　///////////////////////////////////////////////////////////////////////////////
/* Shuts down the socket.
*/
　　void shutdown_socket( int sockfd )
{
  shutdown( sockfd, 2 );
  close( sockfd );
}
　　DWORD WINAPI ClientThread(LPVOID lpParameter)
{
    SOCKET CientSocket = (SOCKET)lpParameter;
    int Ret = 0;
    char RecvBuffer[1024];
　　while ( 1 )
    {
        memset(RecvBuffer, 0x00, sizeof(RecvBuffer));
        Ret = recv(CientSocket, RecvBuffer, 1024, 0);
        if ( Ret == 0 || Ret == SOCKET_ERROR )
        {
            printf("服务端退出!");
            break;
        }
        
    }
printf("接收到服务端的信息为%s", RecvBuffer);
　　return 0;
}
　　
int main(int argc, char * argv[])
{
    WSADATA Ws;
    SOCKET ClientSocket;
    struct sockaddr_in ServerAddr;
    int Ret = 0;
    int AddrLen = 0;
    HANDLE hThread = NULL;
    char SendBuffer[MAX_PATH];
int str_len;
char RecvBuffer[30];
　　//Init Windows Socket
    if ( WSAStartup(MAKEWORD(2,2), &Ws) != 0 )
    {
        printf("Init Windows Socket Failed");
        return -1;
    }
    //Create Socket
    ClientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if ( ClientSocket == INVALID_SOCKET )
    {
        printf("Create Socket Failed");
        return -1;
    }
　　ServerAddr.sin_family = AF_INET;
    ServerAddr.sin_addr.s_addr = inet_addr(IP_ADDRESS);
    ServerAddr.sin_port = htons(PORT);
    memset(ServerAddr.sin_zero, 0x00, 8);
　　Ret = connect(ClientSocket,(struct sockaddr*)&ServerAddr, sizeof(ServerAddr));
    if ( Ret == SOCKET_ERROR )
    {
        printf("Connect Error");
        return -1;
    }
    else
    {
        printf("连接成功!\n");
    }
　　//read(ClientSocket, RecvBuffer, sizeof(RecvBuffer) - 1);
str_len = recv(ClientSocket, RecvBuffer, 30, 0);
RecvBuffer[str_len] = '\0';
printf("Message from server: %s\n", RecvBuffer);
　　while ( 1 )
    {
        //cin.getline(SendBuffer, sizeof(SendBuffer));
printf("Enter the Send infos-\n");
        scanf("%s", SendBuffer);
        Ret = send(ClientSocket, SendBuffer, (int)strlen(SendBuffer), 0);
        if ( Ret == SOCKET_ERROR )
        {
            printf("Send Info Error");
            break;
        }
　　/*
        hThread = CreateThread(NULL, 0, ClientThread, (LPVOID)ClientSocket, 0, NULL);
        if ( hThread == NULL )
        {
            printf("Create Thread Failed!");
            break;
        }
　　CloseHandle(hThread);
*/
        printf("开始接收！");
//str_len = read(ClientSocket, RecvBuffer, sizeof(RecvBuffer) - 1);
//str_len = read(ClientSocket, RecvBuffer, sizeof(RecvBuffer) - 1);
//str_len = read(ClientSocket, RecvBuffer, sizeof(RecvBuffer) - 1);
str_len = recv(ClientSocket, RecvBuffer, 30, 0);
if (str_len == -1)
printf("read() error!");
else
printf("接受到的返回消息：%s",RecvBuffer);
    }
　　closesocket(ClientSocket);
    WSACleanup();
　　return 0;
}